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2023-11-28net: annotate data-races around sk->sk_dst_pending_confirmEric Dumazet1-1/+1
[ Upstream commit eb44ad4e635132754bfbcb18103f1dcb7058aedd ] This field can be read or written without socket lock being held. Add annotations to avoid load-store tearing. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-03-22tcp: tcp_make_synack() can be called from process contextBreno Leitao1-1/+1
[ Upstream commit bced3f7db95ff2e6ca29dc4d1c9751ab5e736a09 ] tcp_rtx_synack() now could be called in process context as explained in 0a375c822497 ("tcp: tcp_rtx_synack() can be called from process context"). tcp_rtx_synack() might call tcp_make_synack(), which will touch per-CPU variables with preemption enabled. This causes the following BUG: BUG: using __this_cpu_add() in preemptible [00000000] code: ThriftIO1/5464 caller is tcp_make_synack+0x841/0xac0 Call Trace: <TASK> dump_stack_lvl+0x10d/0x1a0 check_preemption_disabled+0x104/0x110 tcp_make_synack+0x841/0xac0 tcp_v6_send_synack+0x5c/0x450 tcp_rtx_synack+0xeb/0x1f0 inet_rtx_syn_ack+0x34/0x60 tcp_check_req+0x3af/0x9e0 tcp_rcv_state_process+0x59b/0x2030 tcp_v6_do_rcv+0x5f5/0x700 release_sock+0x3a/0xf0 tcp_sendmsg+0x33/0x40 ____sys_sendmsg+0x2f2/0x490 __sys_sendmsg+0x184/0x230 do_syscall_64+0x3d/0x90 Avoid calling __TCP_INC_STATS() with will touch per-cpu variables. Use TCP_INC_STATS() which is safe to be called from context switch. Fixes: 8336886f786f ("tcp: TCP Fast Open Server - support TFO listeners") Signed-off-by: Breno Leitao <leitao@debian.org> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/20230308190745.780221-1-leitao@debian.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-10-26tcp: fix tcp_cwnd_validate() to not forget is_cwnd_limitedNeal Cardwell1-7/+12
[ Upstream commit f4ce91ce12a7c6ead19b128ffa8cff6e3ded2a14 ] This commit fixes a bug in the tracking of max_packets_out and is_cwnd_limited. This bug can cause the connection to fail to remember that is_cwnd_limited is true, causing the connection to fail to grow cwnd when it should, causing throughput to be lower than it should be. The following event sequence is an example that triggers the bug: (a) The connection is cwnd_limited, but packets_out is not at its peak due to TSO deferral deciding not to send another skb yet. In such cases the connection can advance max_packets_seq and set tp->is_cwnd_limited to true and max_packets_out to a small number. (b) Then later in the round trip the connection is pacing-limited (not cwnd-limited), and packets_out is larger. In such cases the connection would raise max_packets_out to a bigger number but (unexpectedly) flip tp->is_cwnd_limited from true to false. This commit fixes that bug. One straightforward fix would be to separately track (a) the next window after max_packets_out reaches a maximum, and (b) the next window after tp->is_cwnd_limited is set to true. But this would require consuming an extra u32 sequence number. Instead, to save space we track only the most important information. Specifically, we track the strongest available signal of the degree to which the cwnd is fully utilized: (1) If the connection is cwnd-limited then we remember that fact for the current window. (2) If the connection not cwnd-limited then we track the maximum number of outstanding packets in the current window. In particular, note that the new logic cannot trigger the buggy (a)/(b) sequence above because with the new logic a condition where tp->packets_out > tp->max_packets_out can only trigger an update of tp->is_cwnd_limited if tp->is_cwnd_limited is false. This first showed up in a testing of a BBRv2 dev branch, but this buggy behavior highlighted a general issue with the tcp_cwnd_validate() logic that can cause cwnd to fail to increase at the proper rate for any TCP congestion control, including Reno or CUBIC. Fixes: ca8a22634381 ("tcp: make cwnd-limited checks measurement-based, and gentler") Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Kevin(Yudong) Yang <yyd@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-08-25tcp: fix over estimation in sk_forced_mem_schedule()Eric Dumazet1-3/+4
commit c4ee118561a0f74442439b7b5b486db1ac1ddfeb upstream. sk_forced_mem_schedule() has a bug similar to ones fixed in commit 7c80b038d23e ("net: fix sk_wmem_schedule() and sk_rmem_schedule() errors") While this bug has little chance to trigger in old kernels, we need to fix it before the following patch. Fixes: d83769a580f1 ("tcp: fix possible deadlock in tcp_send_fin()") Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Reviewed-by: Shakeel Butt <shakeelb@google.com> Reviewed-by: Wei Wang <weiwan@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-08-25tcp: make retransmitted SKB fit into the send windowYonglong Li1-7/+16
[ Upstream commit 536a6c8e05f95e3d1118c40ae8b3022ee2d05d52 ] current code of __tcp_retransmit_skb only check TCP_SKB_CB(skb)->seq in send window, and TCP_SKB_CB(skb)->seq_end maybe out of send window. If receiver has shrunk his window, and skb is out of new window, it should retransmit a smaller portion of the payload. test packetdrill script: 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR) +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress) +0 > S 0:0(0) win 65535 <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8> +.05 < S. 0:0(0) ack 1 win 6000 <mss 1000,nop,nop,sackOK> +0 > . 1:1(0) ack 1 +0 write(3, ..., 10000) = 10000 +0 > . 1:2001(2000) ack 1 win 65535 +0 > . 2001:4001(2000) ack 1 win 65535 +0 > . 4001:6001(2000) ack 1 win 65535 +.05 < . 1:1(0) ack 4001 win 1001 and tcpdump show: 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 1:2001, ack 1, win 65535, length 2000 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 2001:4001, ack 1, win 65535, length 2000 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000 192.0.2.1.8080 > 192.168.226.67.55: Flags [.], ack 4001, win 1001, length 0 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000 when cient retract window to 1001, send window is [4001,5002], but TLP send 5001-6001 packet which is out of send window. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Yonglong Li <liyonglong@chinatelecom.cn> Signed-off-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/1657532838-20200-1-git-send-email-liyonglong@chinatelecom.cn Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-07-29tcp: Fix a data-race around sysctl_tcp_probe_interval.Kuniyuki Iwashima1-1/+1
[ Upstream commit 2a85388f1d94a9f8b5a529118a2c5eaa0520d85c ] While reading sysctl_tcp_probe_interval, it can be changed concurrently. Thus, we need to add READ_ONCE() to its reader. Fixes: 05cbc0db03e8 ("ipv4: Create probe timer for tcp PMTU as per RFC4821") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-07-29tcp: Fix a data-race around sysctl_tcp_probe_threshold.Kuniyuki Iwashima1-1/+1
[ Upstream commit 92c0aa4175474483d6cf373314343d4e624e882a ] While reading sysctl_tcp_probe_threshold, it can be changed concurrently. Thus, we need to add READ_ONCE() to its reader. Fixes: 6b58e0a5f32d ("ipv4: Use binary search to choose tcp PMTU probe_size") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-06-14tcp: tcp_rtx_synack() can be called from process contextEric Dumazet1-2/+2
[ Upstream commit 0a375c822497ed6ad6b5da0792a12a6f1af10c0b ] Laurent reported the enclosed report [1] This bug triggers with following coditions: 0) Kernel built with CONFIG_DEBUG_PREEMPT=y 1) A new passive FastOpen TCP socket is created. This FO socket waits for an ACK coming from client to be a complete ESTABLISHED one. 2) A socket operation on this socket goes through lock_sock() release_sock() dance. 3) While the socket is owned by the user in step 2), a retransmit of the SYN is received and stored in socket backlog. 4) At release_sock() time, the socket backlog is processed while in process context. 5) A SYNACK packet is cooked in response of the SYN retransmit. 6) -> tcp_rtx_synack() is called in process context. Before blamed commit, tcp_rtx_synack() was always called from BH handler, from a timer handler. Fix this by using TCP_INC_STATS() & NET_INC_STATS() which do not assume caller is in non preemptible context. [1] BUG: using __this_cpu_add() in preemptible [00000000] code: epollpep/2180 caller is tcp_rtx_synack.part.0+0x36/0xc0 CPU: 10 PID: 2180 Comm: epollpep Tainted: G OE 5.16.0-0.bpo.4-amd64 #1 Debian 5.16.12-1~bpo11+1 Hardware name: Supermicro SYS-5039MC-H8TRF/X11SCD-F, BIOS 1.7 11/23/2021 Call Trace: <TASK> dump_stack_lvl+0x48/0x5e check_preemption_disabled+0xde/0xe0 tcp_rtx_synack.part.0+0x36/0xc0 tcp_rtx_synack+0x8d/0xa0 ? kmem_cache_alloc+0x2e0/0x3e0 ? apparmor_file_alloc_security+0x3b/0x1f0 inet_rtx_syn_ack+0x16/0x30 tcp_check_req+0x367/0x610 tcp_rcv_state_process+0x91/0xf60 ? get_nohz_timer_target+0x18/0x1a0 ? lock_timer_base+0x61/0x80 ? preempt_count_add+0x68/0xa0 tcp_v4_do_rcv+0xbd/0x270 __release_sock+0x6d/0xb0 release_sock+0x2b/0x90 sock_setsockopt+0x138/0x1140 ? __sys_getsockname+0x7e/0xc0 ? aa_sk_perm+0x3e/0x1a0 __sys_setsockopt+0x198/0x1e0 __x64_sys_setsockopt+0x21/0x30 do_syscall_64+0x38/0xc0 entry_SYSCALL_64_after_hwframe+0x44/0xae Fixes: 168a8f58059a ("tcp: TCP Fast Open Server - main code path") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Laurent Fasnacht <laurent.fasnacht@proton.ch> Acked-by: Neal Cardwell <ncardwell@google.com> Link: https://lore.kernel.org/r/20220530213713.601888-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-05-12tcp: fix potential xmit stalls caused by TCP_NOTSENT_LOWATEric Dumazet1-0/+1
[ Upstream commit 4bfe744ff1644fbc0a991a2677dc874475dd6776 ] I had this bug sitting for too long in my pile, it is time to fix it. Thanks to Doug Porter for reminding me of it! We had various attempts in the past, including commit 0cbe6a8f089e ("tcp: remove SOCK_QUEUE_SHRUNK"), but the issue is that TCP stack currently only generates EPOLLOUT from input path, when tp->snd_una has advanced and skb(s) cleaned from rtx queue. If a flow has a big RTT, and/or receives SACKs, it is possible that the notsent part (tp->write_seq - tp->snd_nxt) reaches 0 and no more data can be sent until tp->snd_una finally advances. What is needed is to also check if POLLOUT needs to be generated whenever tp->snd_nxt is advanced, from output path. This bug triggers more often after an idle period, as we do not receive ACK for at least one RTT. tcp_notsent_lowat could be a fraction of what CWND and pacing rate would allow to send during this RTT. In a followup patch, I will remove the bogus call to tcp_chrono_stop(sk, TCP_CHRONO_SNDBUF_LIMITED) from tcp_check_space(). Fact that we have decided to generate an EPOLLOUT does not mean the application has immediately refilled the transmit queue. This optimistic call might have been the reason the bug seemed not too serious. Tested: 200 ms rtt, 1% packet loss, 32 MB tcp_rmem[2] and tcp_wmem[2] $ echo 500000 >/proc/sys/net/ipv4/tcp_notsent_lowat $ cat bench_rr.sh SUM=0 for i in {1..10} do V=`netperf -H remote_host -l30 -t TCP_RR -- -r 10000000,10000 -o LOCAL_BYTES_SENT | egrep -v "MIGRATED|Bytes"` echo $V SUM=$(($SUM + $V)) done echo SUM=$SUM Before patch: $ bench_rr.sh 130000000 80000000 140000000 140000000 140000000 140000000 130000000 40000000 90000000 110000000 SUM=1140000000 After patch: $ bench_rr.sh 430000000 590000000 530000000 450000000 450000000 350000000 450000000 490000000 480000000 460000000 SUM=4680000000 # This is 410 % of the value before patch. Fixes: c9bee3b7fdec ("tcp: TCP_NOTSENT_LOWAT socket option") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Doug Porter <dsp@fb.com> Cc: Soheil Hassas Yeganeh <soheil@google.com> Cc: Neal Cardwell <ncardwell@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-04-20tcp: ensure PMTU updates are processed during fastopenJakub Kicinski1-1/+4
[ Upstream commit ed0c99dc0f499ff8b6e75b5ae6092ab42be1ad39 ] tp->rx_opt.mss_clamp is not populated, yet, during TFO send so we rise it to the local MSS. tp->mss_cache is not updated, however: tcp_v6_connect(): tp->rx_opt.mss_clamp = IPV6_MIN_MTU - headers; tcp_connect(): tcp_connect_init(): tp->mss_cache = min(mtu, tp->rx_opt.mss_clamp) tcp_send_syn_data(): tp->rx_opt.mss_clamp = tp->advmss After recent fixes to ICMPv6 PTB handling we started dropping PMTU updates higher than tp->mss_cache. Because of the stale tp->mss_cache value PMTU updates during TFO are always dropped. Thanks to Wei for helping zero in on the problem and the fix! Fixes: c7bb4b89033b ("ipv6: tcp: drop silly ICMPv6 packet too big messages") Reported-by: Andre Nash <alnash@fb.com> Reported-by: Neil Spring <ntspring@fb.com> Reviewed-by: Wei Wang <weiwan@google.com> Acked-by: Yuchung Cheng <ycheng@google.com> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/20220321165957.1769954-1-kuba@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-28ipv6: tcp: drop silly ICMPv6 packet too big messagesEric Dumazet1-0/+1
commit c7bb4b89033b764eb07db4e060548a6311d801ee upstream. While TCP stack scales reasonably well, there is still one part that can be used to DDOS it. IPv6 Packet too big messages have to lookup/insert a new route, and if abused by attackers, can easily put hosts under high stress, with many cpus contending on a spinlock while one is stuck in fib6_run_gc() ip6_protocol_deliver_rcu() icmpv6_rcv() icmpv6_notify() tcp_v6_err() tcp_v6_mtu_reduced() inet6_csk_update_pmtu() ip6_rt_update_pmtu() __ip6_rt_update_pmtu() ip6_rt_cache_alloc() ip6_dst_alloc() dst_alloc() ip6_dst_gc() fib6_run_gc() spin_lock_bh() ... Some of our servers have been hit by malicious ICMPv6 packets trying to _increase_ the MTU/MSS of TCP flows. We believe these ICMPv6 packets are a result of a bug in one ISP stack, since they were blindly sent back for _every_ (small) packet sent to them. These packets are for one TCP flow: 09:24:36.266491 IP6 Addr1 > Victim ICMP6, packet too big, mtu 1460, length 1240 09:24:36.266509 IP6 Addr1 > Victim ICMP6, packet too big, mtu 1460, length 1240 09:24:36.316688 IP6 Addr1 > Victim ICMP6, packet too big, mtu 1460, length 1240 09:24:36.316704 IP6 Addr1 > Victim ICMP6, packet too big, mtu 1460, length 1240 09:24:36.608151 IP6 Addr1 > Victim ICMP6, packet too big, mtu 1460, length 1240 TCP stack can filter some silly requests : 1) MTU below IPV6_MIN_MTU can be filtered early in tcp_v6_err() 2) tcp_v6_mtu_reduced() can drop requests trying to increase current MSS. This tests happen before the IPv6 routing stack is entered, thus removing the potential contention and route exhaustion. Note that IPv6 stack was performing these checks, but too late (ie : after the route has been added, and after the potential garbage collect war) v2: fix typo caught by Martin, thanks ! v3: exports tcp_mtu_to_mss(), caught by David, thanks ! Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Maciej Żenczykowski <maze@google.com> Cc: Martin KaFai Lau <kafai@fb.com> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-12-29tcp: fix cwnd-limited bug for TSO deferral where we send nothingNeal Cardwell1-3/+6
[ Upstream commit 299bcb55ecd1412f6df606e9dc0912d55610029e ] When cwnd is not a multiple of the TSO skb size of N*MSS, we can get into persistent scenarios where we have the following sequence: (1) ACK for full-sized skb of N*MSS arrives -> tcp_write_xmit() transmit full-sized skb with N*MSS -> move pacing release time forward -> exit tcp_write_xmit() because pacing time is in the future (2) TSQ callback or TCP internal pacing timer fires -> try to transmit next skb, but TSO deferral finds remainder of available cwnd is not big enough to trigger an immediate send now, so we defer sending until the next ACK. (3) repeat... So we can get into a case where we never mark ourselves as cwnd-limited for many seconds at a time, even with bulk/infinite-backlog senders, because: o In case (1) above, every time in tcp_write_xmit() we have enough cwnd to send a full-sized skb, we are not fully using the cwnd (because cwnd is not a multiple of the TSO skb size). So every time we send data, we are not cwnd limited, and so in the cwnd-limited tracking code in tcp_cwnd_validate() we mark ourselves as not cwnd-limited. o In case (2) above, every time in tcp_write_xmit() that we try to transmit the "remainder" of the cwnd but defer, we set the local variable is_cwnd_limited to true, but we do not send any packets, so sent_pkts is zero, so we don't call the cwnd-limited logic to update tp->is_cwnd_limited. Fixes: ca8a22634381 ("tcp: make cwnd-limited checks measurement-based, and gentler") Reported-by: Ingemar Johansson <ingemar.s.johansson@ericsson.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/20201209035759.1225145-1-ncardwell.kernel@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-07-31tcp: allow at most one TLP probe per flightYuchung Cheng1-5/+8
[ Upstream commit 76be93fc0702322179bb0ea87295d820ee46ad14 ] Previously TLP may send multiple probes of new data in one flight. This happens when the sender is cwnd limited. After the initial TLP containing new data is sent, the sender receives another ACK that acks partial inflight. It may re-arm another TLP timer to send more, if no further ACK returns before the next TLP timeout (PTO) expires. The sender may send in theory a large amount of TLP until send queue is depleted. This only happens if the sender sees such irregular uncommon ACK pattern. But it is generally undesirable behavior during congestion especially. The original TLP design restrict only one TLP probe per inflight as published in "Reducing Web Latency: the Virtue of Gentle Aggression", SIGCOMM 2013. This patch changes TLP to send at most one probe per inflight. Note that if the sender is app-limited, TLP retransmits old data and did not have this issue. Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-07-22tcp: md5: do not send silly options in SYNCOOKIESEric Dumazet1-4/+6
[ Upstream commit e114e1e8ac9d31f25b9dd873bab5d80c1fc482ca ] Whenever cookie_init_timestamp() has been used to encode ECN,SACK,WSCALE options, we can not remove the TS option in the SYNACK. Otherwise, tcp_synack_options() will still advertize options like WSCALE that we can not deduce later when receiving the packet from the client to complete 3WHS. Note that modern linux TCP stacks wont use MD5+TS+SACK in a SYN packet, but we can not know for sure that all TCP stacks have the same logic. Before the fix a tcpdump would exhibit this wrong exchange : 10:12:15.464591 IP C > S: Flags [S], seq 4202415601, win 65535, options [nop,nop,md5 valid,mss 1400,sackOK,TS val 456965269 ecr 0,nop,wscale 8], length 0 10:12:15.464602 IP S > C: Flags [S.], seq 253516766, ack 4202415602, win 65535, options [nop,nop,md5 valid,mss 1400,nop,nop,sackOK,nop,wscale 8], length 0 10:12:15.464611 IP C > S: Flags [.], ack 1, win 256, options [nop,nop,md5 valid], length 0 10:12:15.464678 IP C > S: Flags [P.], seq 1:13, ack 1, win 256, options [nop,nop,md5 valid], length 12 10:12:15.464685 IP S > C: Flags [.], ack 13, win 65535, options [nop,nop,md5 valid], length 0 After this patch the exchange looks saner : 11:59:59.882990 IP C > S: Flags [S], seq 517075944, win 65535, options [nop,nop,md5 valid,mss 1400,sackOK,TS val 1751508483 ecr 0,nop,wscale 8], length 0 11:59:59.883002 IP S > C: Flags [S.], seq 1902939253, ack 517075945, win 65535, options [nop,nop,md5 valid,mss 1400,sackOK,TS val 1751508479 ecr 1751508483,nop,wscale 8], length 0 11:59:59.883012 IP C > S: Flags [.], ack 1, win 256, options [nop,nop,md5 valid,nop,nop,TS val 1751508483 ecr 1751508479], length 0 11:59:59.883114 IP C > S: Flags [P.], seq 1:13, ack 1, win 256, options [nop,nop,md5 valid,nop,nop,TS val 1751508483 ecr 1751508479], length 12 11:59:59.883122 IP S > C: Flags [.], ack 13, win 256, options [nop,nop,md5 valid,nop,nop,TS val 1751508483 ecr 1751508483], length 0 11:59:59.883152 IP S > C: Flags [P.], seq 1:13, ack 13, win 256, options [nop,nop,md5 valid,nop,nop,TS val 1751508484 ecr 1751508483], length 12 11:59:59.883170 IP C > S: Flags [.], ack 13, win 256, options [nop,nop,md5 valid,nop,nop,TS val 1751508484 ecr 1751508484], length 0 Of course, no SACK block will ever be added later, but nothing should break. Technically, we could remove the 4 nops included in MD5+TS options, but again some stacks could break seeing not conventional alignment. Fixes: 4957faade11b ("TCPCT part 1g: Responder Cookie => Initiator") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Florian Westphal <fw@strlen.de> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-01-04tcp: do not send empty skb from tcp_write_xmit()Eric Dumazet1-0/+8
[ Upstream commit 1f85e6267caca44b30c54711652b0726fadbb131 ] Backport of commit fdfc5c8594c2 ("tcp: remove empty skb from write queue in error cases") in linux-4.14 stable triggered various bugs. One of them has been fixed in commit ba2ddb43f270 ("tcp: Don't dequeue SYN/FIN-segments from write-queue"), but we still have crashes in some occasions. Root-cause is that when tcp_sendmsg() has allocated a fresh skb and could not append a fragment before being blocked in sk_stream_wait_memory(), tcp_write_xmit() might be called and decide to send this fresh and empty skb. Sending an empty packet is not only silly, it might have caused many issues we had in the past with tp->packets_out being out of sync. Fixes: c65f7f00c587 ("[TCP]: Simplify SKB data portion allocation with NETIF_F_SG.") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Christoph Paasch <cpaasch@apple.com> Acked-by: Neal Cardwell <ncardwell@google.com> Cc: Jason Baron <jbaron@akamai.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-12-21tcp: md5: fix potential overestimation of TCP option spaceEric Dumazet1-2/+3
[ Upstream commit 9424e2e7ad93ffffa88f882c9bc5023570904b55 ] Back in 2008, Adam Langley fixed the corner case of packets for flows having all of the following options : MD5 TS SACK Since MD5 needs 20 bytes, and TS needs 12 bytes, no sack block can be cooked from the remaining 8 bytes. tcp_established_options() correctly sets opts->num_sack_blocks to zero, but returns 36 instead of 32. This means TCP cooks packets with 4 extra bytes at the end of options, containing unitialized bytes. Fixes: 33ad798c924b ("tcp: options clean up") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-12-17tcp: fix SNMP under-estimation on failed retransmissionYuchung Cheng1-1/+1
[ Upstream commit ec641b39457e17774313b66697a8a1dc070257bd ] Previously the SNMP counter LINUX_MIB_TCPRETRANSFAIL is not counting the TSO/GSO properly on failed retransmission. This patch fixes that. Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
2019-09-10tcp: inherit timestamp on mtu probeWillem de Bruijn1-1/+2
[ Upstream commit 888a5c53c0d8be6e98bc85b677f179f77a647873 ] TCP associates tx timestamp requests with a byte in the bytestream. If merging skbs in tcp_mtu_probe, migrate the tstamp request. Similar to MSG_EOR, do not allow moving a timestamp from any segment in the probe but the last. This to avoid merging multiple timestamps. Tested with the packetdrill script at https://github.com/wdebruij/packetdrill/commits/mtu_probe-1 Link: http://patchwork.ozlabs.org/patch/1143278/#2232897 Fixes: 4ed2d765dfac ("net-timestamp: TCP timestamping") Signed-off-by: Willem de Bruijn <willemb@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-08-09tcp: be more careful in tcp_fragment()Eric Dumazet1-1/+10
commit b617158dc096709d8600c53b6052144d12b89fab upstream. Some applications set tiny SO_SNDBUF values and expect TCP to just work. Recent patches to address CVE-2019-11478 broke them in case of losses, since retransmits might be prevented. We should allow these flows to make progress. This patch allows the first and last skb in retransmit queue to be split even if memory limits are hit. It also adds the some room due to the fact that tcp_sendmsg() and tcp_sendpage() might overshoot sk_wmem_queued by about one full TSO skb (64KB size). Note this allowance was already present in stable backports for kernels < 4.15 Note for < 4.15 backports : tcp_rtx_queue_tail() will probably look like : static inline struct sk_buff *tcp_rtx_queue_tail(const struct sock *sk) { struct sk_buff *skb = tcp_send_head(sk); return skb ? tcp_write_queue_prev(sk, skb) : tcp_write_queue_tail(sk); } Fixes: f070ef2ac667 ("tcp: tcp_fragment() should apply sane memory limits") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Andrew Prout <aprout@ll.mit.edu> Tested-by: Andrew Prout <aprout@ll.mit.edu> Tested-by: Jonathan Lemon <jonathan.lemon@gmail.com> Tested-by: Michal Kubecek <mkubecek@suse.cz> Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Yuchung Cheng <ycheng@google.com> Acked-by: Christoph Paasch <cpaasch@apple.com> Cc: Jonathan Looney <jtl@netflix.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
2019-06-27tcp: refine memory limit test in tcp_fragment()Eric Dumazet1-1/+1
commit b6653b3629e5b88202be3c9abc44713973f5c4b4 upstream. tcp_fragment() might be called for skbs in the write queue. Memory limits might have been exceeded because tcp_sendmsg() only checks limits at full skb (64KB) boundaries. Therefore, we need to make sure tcp_fragment() wont punish applications that might have setup very low SO_SNDBUF values. Fixes: f070ef2ac667 ("tcp: tcp_fragment() should apply sane memory limits") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Christoph Paasch <cpaasch@apple.com> Tested-by: Christoph Paasch <cpaasch@apple.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-06-17tcp: add tcp_min_snd_mss sysctlEric Dumazet1-2/+1
commit 5f3e2bf008c2221478101ee72f5cb4654b9fc363 upstream. Some TCP peers announce a very small MSS option in their SYN and/or SYN/ACK messages. This forces the stack to send packets with a very high network/cpu overhead. Linux has enforced a minimal value of 48. Since this value includes the size of TCP options, and that the options can consume up to 40 bytes, this means that each segment can include only 8 bytes of payload. In some cases, it can be useful to increase the minimal value to a saner value. We still let the default to 48 (TCP_MIN_SND_MSS), for compatibility reasons. Note that TCP_MAXSEG socket option enforces a minimal value of (TCP_MIN_MSS). David Miller increased this minimal value in commit c39508d6f118 ("tcp: Make TCP_MAXSEG minimum more correct.") from 64 to 88. We might in the future merge TCP_MIN_SND_MSS and TCP_MIN_MSS. CVE-2019-11479 -- tcp mss hardcoded to 48 Signed-off-by: Eric Dumazet <edumazet@google.com> Suggested-by: Jonathan Looney <jtl@netflix.com> Acked-by: Neal Cardwell <ncardwell@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Tyler Hicks <tyhicks@canonical.com> Cc: Bruce Curtis <brucec@netflix.com> Cc: Jonathan Lemon <jonathan.lemon@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-06-17tcp: tcp_fragment() should apply sane memory limitsEric Dumazet1-0/+5
commit f070ef2ac66716357066b683fb0baf55f8191a2e upstream. Jonathan Looney reported that a malicious peer can force a sender to fragment its retransmit queue into tiny skbs, inflating memory usage and/or overflow 32bit counters. TCP allows an application to queue up to sk_sndbuf bytes, so we need to give some allowance for non malicious splitting of retransmit queue. A new SNMP counter is added to monitor how many times TCP did not allow to split an skb if the allowance was exceeded. Note that this counter might increase in the case applications use SO_SNDBUF socket option to lower sk_sndbuf. CVE-2019-11478 : tcp_fragment, prevent fragmenting a packet when the socket is already using more than half the allowed space Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Jonathan Looney <jtl@netflix.com> Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Yuchung Cheng <ycheng@google.com> Reviewed-by: Tyler Hicks <tyhicks@canonical.com> Cc: Bruce Curtis <brucec@netflix.com> Cc: Jonathan Lemon <jonathan.lemon@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-06-17tcp: limit payload size of sacked skbsEric Dumazet1-3/+3
commit 3b4929f65b0d8249f19a50245cd88ed1a2f78cff upstream. Jonathan Looney reported that TCP can trigger the following crash in tcp_shifted_skb() : BUG_ON(tcp_skb_pcount(skb) < pcount); This can happen if the remote peer has advertized the smallest MSS that linux TCP accepts : 48 An skb can hold 17 fragments, and each fragment can hold 32KB on x86, or 64KB on PowerPC. This means that the 16bit witdh of TCP_SKB_CB(skb)->tcp_gso_segs can overflow. Note that tcp_sendmsg() builds skbs with less than 64KB of payload, so this problem needs SACK to be enabled. SACK blocks allow TCP to coalesce multiple skbs in the retransmit queue, thus filling the 17 fragments to maximal capacity. CVE-2019-11477 -- u16 overflow of TCP_SKB_CB(skb)->tcp_gso_segs Backport notes, provided by Joao Martins <joao.m.martins@oracle.com> v4.15 or since commit 737ff314563 ("tcp: use sequence distance to detect reordering") had switched from the packet-based FACK tracking and switched to sequence-based. v4.14 and older still have the old logic and hence on tcp_skb_shift_data() needs to retain its original logic and have @fack_count in sync. In other words, we keep the increment of pcount with tcp_skb_pcount(skb) to later used that to update fack_count. To make it more explicit we track the new skb that gets incremented to pcount in @next_pcount, and we get to avoid the constant invocation of tcp_skb_pcount(skb) all together. Fixes: 832d11c5cd07 ("tcp: Try to restore large SKBs while SACK processing") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Jonathan Looney <jtl@netflix.com> Acked-by: Neal Cardwell <ncardwell@google.com> Reviewed-by: Tyler Hicks <tyhicks@canonical.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Bruce Curtis <brucec@netflix.com> Cc: Jonathan Lemon <jonathan.lemon@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-12-17tcp: lack of available data can also cause TSO deferEric Dumazet1-11/+24
commit f9bfe4e6a9d08d405fe7b081ee9a13e649c97ecf upstream. tcp_tso_should_defer() can return true in three different cases : 1) We are cwnd-limited 2) We are rwnd-limited 3) We are application limited. Neal pointed out that my recent fix went too far, since it assumed that if we were not in 1) case, we must be rwnd-limited Fix this by properly populating the is_cwnd_limited and is_rwnd_limited booleans. After this change, we can finally move the silly check for FIN flag only for the application-limited case. The same move for EOR bit will be handled in net-next, since commit 1c09f7d073b1 ("tcp: do not try to defer skbs with eor mark (MSG_EOR)") is scheduled for linux-4.21 Tested by running 200 concurrent netperf -t TCP_RR -- -r 60000,100 and checking none of them was rwnd_limited in the chrono_stat output from "ss -ti" command. Fixes: 41727549de3e ("tcp: Do not underestimate rwnd_limited") Signed-off-by: Eric Dumazet <edumazet@google.com> Suggested-by: Neal Cardwell <ncardwell@google.com> Reviewed-by: Neal Cardwell <ncardwell@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Reviewed-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-12-17tcp: fix NULL ref in tail loss probeYuchung Cheng1-4/+8
[ Upstream commit b2b7af861122a0c0f6260155c29a1b2e594cd5b5 ] TCP loss probe timer may fire when the retranmission queue is empty but has a non-zero tp->packets_out counter. tcp_send_loss_probe will call tcp_rearm_rto which triggers NULL pointer reference by fetching the retranmission queue head in its sub-routines. Add a more detailed warning to help catch the root cause of the inflight accounting inconsistency. Reported-by: Rafael Tinoco <rafael.tinoco@linaro.org> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-12-17tcp: Do not underestimate rwnd_limitedEric Dumazet1-1/+4
[ Upstream commit 41727549de3e7281feb174d568c6e46823db8684 ] If available rwnd is too small, tcp_tso_should_defer() can decide it is worth waiting before splitting a TSO packet. This really means we are rwnd limited. Fixes: 5615f88614a4 ("tcp: instrument how long TCP is limited by receive window") Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Reviewed-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-08-24tcp: remove DELAYED ACK events in DCTCPYuchung Cheng1-4/+0
[ Upstream commit a69258f7aa2623e0930212f09c586fd06674ad79 ] After fixing the way DCTCP tracking delayed ACKs, the delayed-ACK related callbacks are no longer needed Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Lawrence Brakmo <brakmo@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-07-28tcp: do not cancel delay-AcK on DCTCP special ACKYuchung Cheng1-3/+8
[ Upstream commit 27cde44a259c380a3c09066fc4b42de7dde9b1ad ] Currently when a DCTCP receiver delays an ACK and receive a data packet with a different CE mark from the previous one's, it sends two immediate ACKs acking previous and latest sequences respectly (for ECN accounting). Previously sending the first ACK may mark off the delayed ACK timer (tcp_event_ack_sent). This may subsequently prevent sending the second ACK to acknowledge the latest sequence (tcp_ack_snd_check). The culprit is that tcp_send_ack() assumes it always acknowleges the latest sequence, which is not true for the first special ACK. The fix is to not make the assumption in tcp_send_ack and check the actual ack sequence before cancelling the delayed ACK. Further it's safer to pass the ack sequence number as a local variable into tcp_send_ack routine, instead of intercepting tp->rcv_nxt to avoid future bugs like this. Reported-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-07-28tcp: helpers to send special DCTCP ackYuchung Cheng1-5/+17
[ Upstream commit 2987babb6982306509380fc11b450227a844493b ] Refactor and create helpers to send the special ACK in DCTCP. Signed-off-by: Yuchung Cheng <ycheng@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-05-25tcp: purge write queue in tcp_connect_init()Eric Dumazet1-2/+5
[ Upstream commit 7f582b248d0a86bae5788c548d7bb5bca6f7691a ] syzkaller found a reliable way to crash the host, hitting a BUG() in __tcp_retransmit_skb() Malicous MSG_FASTOPEN is the root cause. We need to purge write queue in tcp_connect_init() at the point we init snd_una/write_seq. This patch also replaces the BUG() by a less intrusive WARN_ON_ONCE() kernel BUG at net/ipv4/tcp_output.c:2837! invalid opcode: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 0 PID: 5276 Comm: syz-executor0 Not tainted 4.17.0-rc3+ #51 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__tcp_retransmit_skb+0x2992/0x2eb0 net/ipv4/tcp_output.c:2837 RSP: 0000:ffff8801dae06ff8 EFLAGS: 00010206 RAX: ffff8801b9fe61c0 RBX: 00000000ffc18a16 RCX: ffffffff864e1a49 RDX: 0000000000000100 RSI: ffffffff864e2e12 RDI: 0000000000000005 RBP: ffff8801dae073a0 R08: ffff8801b9fe61c0 R09: ffffed0039c40dd2 R10: ffffed0039c40dd2 R11: ffff8801ce206e93 R12: 00000000421eeaad R13: ffff8801ce206d4e R14: ffff8801ce206cc0 R15: ffff8801cd4f4a80 FS: 0000000000000000(0000) GS:ffff8801dae00000(0063) knlGS:00000000096bc900 CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 CR2: 0000000020000000 CR3: 00000001c47b6000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> tcp_retransmit_skb+0x2e/0x250 net/ipv4/tcp_output.c:2923 tcp_retransmit_timer+0xc50/0x3060 net/ipv4/tcp_timer.c:488 tcp_write_timer_handler+0x339/0x960 net/ipv4/tcp_timer.c:573 tcp_write_timer+0x111/0x1d0 net/ipv4/tcp_timer.c:593 call_timer_fn+0x230/0x940 kernel/time/timer.c:1326 expire_timers kernel/time/timer.c:1363 [inline] __run_timers+0x79e/0xc50 kernel/time/timer.c:1666 run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692 __do_softirq+0x2e0/0xaf5 kernel/softirq.c:285 invoke_softirq kernel/softirq.c:365 [inline] irq_exit+0x1d1/0x200 kernel/softirq.c:405 exiting_irq arch/x86/include/asm/apic.h:525 [inline] smp_apic_timer_interrupt+0x17e/0x710 arch/x86/kernel/apic/apic.c:1052 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863 Fixes: cf60af03ca4e ("net-tcp: Fast Open client - sendmsg(MSG_FASTOPEN)") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Neal Cardwell <ncardwell@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-03-09tcp_bbr: better deal with suboptimal GSOEric Dumazet1-3/+5
[ Upstream commit 350c9f484bde93ef229682eedd98cd5f74350f7f ] BBR uses tcp_tso_autosize() in an attempt to probe what would be the burst sizes and to adjust cwnd in bbr_target_cwnd() with following gold formula : /* Allow enough full-sized skbs in flight to utilize end systems. */ cwnd += 3 * bbr->tso_segs_goal; But GSO can be lacking or be constrained to very small units (ip link set dev ... gso_max_segs 2) What we really want is to have enough packets in flight so that both GSO and GRO are efficient. So in the case GSO is off or downgraded, we still want to have the same number of packets in flight as if GSO/TSO was fully operational, so that GRO can hopefully be working efficiently. To fix this issue, we make tcp_tso_autosize() unaware of sk->sk_gso_max_segs Only tcp_tso_segs() has to enforce the gso_max_segs limit. Tested: ethtool -K eth0 tso off gso off tc qd replace dev eth0 root pfifo_fast Before patch: for f in {1..5}; do ./super_netperf 1 -H lpaa24 -- -K bbr; done     691  (ss -temoi shows cwnd is stuck around 6 )     667     651     631     517 After patch : # for f in {1..5}; do ./super_netperf 1 -H lpaa24 -- -K bbr; done    1733 (ss -temoi shows cwnd is around 386 )    1778    1746    1781    1718 Fixes: 0f8782ea1497 ("tcp_bbr: add BBR congestion control") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name> Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-03-09tcp: Honor the eor bit in tcp_mtu_probeIlya Lesokhin1-0/+25
[ Upstream commit 808cf9e38cd7923036a99f459ccc8cf2955e47af ] Avoid SKB coalescing if eor bit is set in one of the relevant SKBs. Fixes: c134ecb87817 ("tcp: Make use of MSG_EOR in tcp_sendmsg") Signed-off-by: Ilya Lesokhin <ilyal@mellanox.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-12-17tcp: when scheduling TLP, time of RTO should account for current ACKNeal Cardwell1-3/+5
[ Upstream commit ed66dfaf236c04d414de1d218441296e57fb2bd2 ] Fix the TLP scheduling logic so that when scheduling a TLP probe, we ensure that the estimated time at which an RTO would fire accounts for the fact that ACKs indicating forward progress should push back RTO times. After the following fix: df92c8394e6e ("tcp: fix xmit timer to only be reset if data ACKed/SACKed") we had an unintentional behavior change in the following kind of scenario: suppose the RTT variance has been very low recently. Then suppose we send out a flight of N packets and our RTT is 100ms: t=0: send a flight of N packets t=100ms: receive an ACK for N-1 packets The response before df92c8394e6e that was: -> schedule a TLP for now + RTO_interval The response after df92c8394e6e is: -> schedule a TLP for t=0 + RTO_interval Since RTO_interval = srtt + RTT_variance, this means that we have scheduled a TLP timer at a point in the future that only accounts for RTT_variance. If the RTT_variance term is small, this means that the timer fires soon. Before df92c8394e6e this would not happen, because in that code, when we receive an ACK for a prefix of flight, we did: 1) Near the top of tcp_ack(), switch from TLP timer to RTO at write_queue_head->paket_tx_time + RTO_interval: if (icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) tcp_rearm_rto(sk); 2) In tcp_clean_rtx_queue(), update the RTO to now + RTO_interval: if (flag & FLAG_ACKED) { tcp_rearm_rto(sk); 3) In tcp_ack() after tcp_fastretrans_alert() switch from RTO to TLP at now + RTO_interval: if (icsk->icsk_pending == ICSK_TIME_RETRANS) tcp_schedule_loss_probe(sk); In df92c8394e6e we removed that 3-phase dance, and instead directly set the TLP timer once: we set the TLP timer in cases like this to write_queue_head->packet_tx_time + RTO_interval. So if the RTT variance is small, then this means that this is setting the TLP timer to fire quite soon. This means if the ACK for the tail of the flight takes longer than an RTT to arrive (often due to delayed ACKs), then the TLP timer fires too quickly. Fixes: df92c8394e6e ("tcp: fix xmit timer to only be reset if data ACKed/SACKed") Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-03tcp: do not mangle skb->cb[] in tcp_make_synack()Eric Dumazet1-7/+2
Christoph Paasch sent a patch to address the following issue : tcp_make_synack() is leaving some TCP private info in skb->cb[], then send the packet by other means than tcp_transmit_skb() tcp_transmit_skb() makes sure to clear skb->cb[] to not confuse IPv4/IPV6 stacks, but we have no such cleanup for SYNACK. tcp_make_synack() should not use tcp_init_nondata_skb() : tcp_init_nondata_skb() really should be limited to skbs put in write/rtx queues (the ones that are only sent via tcp_transmit_skb()) This patch fixes the issue and should even save few cpu cycles ;) Fixes: 971f10eca186 ("tcp: better TCP_SKB_CB layout to reduce cache line misses") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Christoph Paasch <cpaasch@apple.com> Reviewed-by: Christoph Paasch <cpaasch@apple.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-11-01tcp: fix tcp_mtu_probe() vs highest_sackEric Dumazet1-1/+2
Based on SNMP values provided by Roman, Yuchung made the observation that some crashes in tcp_sacktag_walk() might be caused by MTU probing. Looking at tcp_mtu_probe(), I found that when a new skb was placed in front of the write queue, we were not updating tcp highest sack. If one skb is freed because all its content was copied to the new skb (for MTU probing), then tp->highest_sack could point to a now freed skb. Bad things would then happen, including infinite loops. This patch renames tcp_highest_sack_combine() and uses it from tcp_mtu_probe() to fix the bug. Note that I also removed one test against tp->sacked_out, since we want to replace tp->highest_sack regardless of whatever condition, since keeping a stale pointer to freed skb is a recipe for disaster. Fixes: a47e5a988a57 ("[TCP]: Convert highest_sack to sk_buff to allow direct access") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com> Reported-by: Roman Gushchin <guro@fb.com> Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-10-28tcp: refresh tp timestamp before tcp_mtu_probe()Eric Dumazet1-1/+1
In the unlikely event tcp_mtu_probe() is sending a packet, we want tp->tcp_mstamp being as accurate as possible. This means we need to call tcp_mstamp_refresh() a bit earlier in tcp_write_xmit(). Fixes: 385e20706fac ("tcp: use tp->tcp_mstamp in output path") Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-10-26tcp: call tcp_rate_skb_sent() when retransmit with unaligned skb->dataYousuk Seung1-1/+3
Current implementation calls tcp_rate_skb_sent() when tcp_transmit_skb() is called when it clones skb only. Not calling tcp_rate_skb_sent() is OK for all such code paths except from __tcp_retransmit_skb() which happens when skb->data address is not aligned. This may rarely happen e.g. when small amount of data is sent initially and the receiver partially acks odd number of bytes for some reason, possibly malicious. Signed-off-by: Yousuk Seung <ysseung@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-10-23tcp: do tcp_mstamp_refresh before retransmits on TSQ handlerKoichiro Den1-1/+3
When retransmission on TSQ handler was introduced in the commit f9616c35a0d7 ("tcp: implement TSQ for retransmits"), the retransmitted skbs' timestamps were updated on the actual transmission. In the later commit 385e20706fac ("tcp: use tp->tcp_mstamp in output path"), it stops being done so. In the commit, the comment says "We try to refresh tp->tcp_mstamp only when necessary", and at present tcp_tsq_handler and tcp_v4_mtu_reduced applies to this. About the latter, it's okay since it's rare enough. About the former, even though possible retransmissions on the tasklet comes just after the destructor run in NET_RX softirq handling, the time between them could be nonnegligibly large to the extent that tcp_rack_advance or rto rearming be affected if other (remaining) RX, BLOCK and (preceding) TASKLET sofirq handlings are unexpectedly heavy. So in the same way as tcp_write_timer_handler does, doing tcp_mstamp_refresh ensures the accuracy of algorithms relying on it. Fixes: 385e20706fac ("tcp: use tp->tcp_mstamp in output path") Signed-off-by: Koichiro Den <den@klaipeden.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-20tcp: fastopen: fix on syn-data transmit failureEric Dumazet1-0/+9
Our recent change exposed a bug in TCP Fastopen Client that syzkaller found right away [1] When we prepare skb with SYN+DATA, we attempt to transmit it, and we update socket state as if the transmit was a success. In socket RTX queue we have two skbs, one with the SYN alone, and a second one containing the DATA. When (malicious) ACK comes in, we now complain that second one had no skb_mstamp. The proper fix is to make sure that if the transmit failed, we do not pretend we sent the DATA skb, and make it our send_head. When 3WHS completes, we can now send the DATA right away, without having to wait for a timeout. [1] WARNING: CPU: 0 PID: 100189 at net/ipv4/tcp_input.c:3117 tcp_clean_rtx_queue+0x2057/0x2ab0 net/ipv4/tcp_input.c:3117() WARN_ON_ONCE(last_ackt == 0); Modules linked in: CPU: 0 PID: 100189 Comm: syz-executor1 Not tainted Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 ffff8800b35cb1d8 ffffffff81cad00d 0000000000000000 ffffffff828a4347 ffff88009f86c080 ffffffff8316eb20 0000000000000d7f ffff8800b35cb220 ffffffff812c33c2 ffff8800baad2440 00000009d46575c0 Call Trace: [<ffffffff81cad00d>] __dump_stack [<ffffffff81cad00d>] dump_stack+0xc1/0x124 [<ffffffff812c33c2>] warn_slowpath_common+0xe2/0x150 [<ffffffff812c361e>] warn_slowpath_null+0x2e/0x40 [<ffffffff828a4347>] tcp_clean_rtx_queue+0x2057/0x2ab0 n [<ffffffff828ae6fd>] tcp_ack+0x151d/0x3930 [<ffffffff828baa09>] tcp_rcv_state_process+0x1c69/0x4fd0 [<ffffffff828efb7f>] tcp_v4_do_rcv+0x54f/0x7c0 [<ffffffff8258aacb>] sk_backlog_rcv [<ffffffff8258aacb>] __release_sock+0x12b/0x3a0 [<ffffffff8258ad9e>] release_sock+0x5e/0x1c0 [<ffffffff8294a785>] inet_wait_for_connect [<ffffffff8294a785>] __inet_stream_connect+0x545/0xc50 [<ffffffff82886f08>] tcp_sendmsg_fastopen [<ffffffff82886f08>] tcp_sendmsg+0x2298/0x35a0 [<ffffffff82952515>] inet_sendmsg+0xe5/0x520 [<ffffffff8257152f>] sock_sendmsg_nosec [<ffffffff8257152f>] sock_sendmsg+0xcf/0x110 Fixes: 8c72c65b426b ("tcp: update skb->skb_mstamp more carefully") Fixes: 783237e8daf1 ("net-tcp: Fast Open client - sending SYN-data") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Yuchung Cheng <ycheng@google.com> Acked-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-19tcp: remove two unused functionsYuchung Cheng1-34/+0
remove tcp_may_send_now and tcp_snd_test that are no longer used Fixes: 840a3cbe8969 ("tcp: remove forward retransmit feature") Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-16tcp: fix data delivery rateEric Dumazet1-4/+3
Now skb->mstamp_skb is updated later, we also need to call tcp_rate_skb_sent() after the update is done. Fixes: 8c72c65b426b ("tcp: update skb->skb_mstamp more carefully") Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-16tcp: update skb->skb_mstamp more carefullyEric Dumazet1-7/+12
liujian reported a problem in TCP_USER_TIMEOUT processing with a patch in tcp_probe_timer() : https://www.spinics.net/lists/netdev/msg454496.html After investigations, the root cause of the problem is that we update skb->skb_mstamp of skbs in write queue, even if the attempt to send a clone or copy of it failed. One reason being a routing problem. This patch prevents this, solving liujian issue. It also removes a potential RTT miscalculation, since __tcp_retransmit_skb() is not OR-ing TCP_SKB_CB(skb)->sacked with TCPCB_EVER_RETRANS if a failure happens, but skb->skb_mstamp has been changed. A future ACK would then lead to a very small RTT sample and min_rtt would then be lowered to this too small value. Tested: # cat user_timeout.pkt --local_ip=192.168.102.64 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 +0 bind(3, ..., ...) = 0 +0 listen(3, 1) = 0 +0 `ifconfig tun0 192.168.102.64/16; ip ro add 192.0.2.1 dev tun0` +0 < S 0:0(0) win 0 <mss 1460> +0 > S. 0:0(0) ack 1 <mss 1460> +.1 < . 1:1(0) ack 1 win 65530 +0 accept(3, ..., ...) = 4 +0 setsockopt(4, SOL_TCP, TCP_USER_TIMEOUT, [3000], 4) = 0 +0 write(4, ..., 24) = 24 +0 > P. 1:25(24) ack 1 win 29200 +.1 < . 1:1(0) ack 25 win 65530 //change the ipaddress +1 `ifconfig tun0 192.168.0.10/16` +1 write(4, ..., 24) = 24 +1 write(4, ..., 24) = 24 +1 write(4, ..., 24) = 24 +1 write(4, ..., 24) = 24 +0 `ifconfig tun0 192.168.102.64/16` +0 < . 1:2(1) ack 25 win 65530 +0 `ifconfig tun0 192.168.0.10/16` +3 write(4, ..., 24) = -1 # ./packetdrill user_timeout.pkt Signed-off-by: Eric Dumazet <edumazet@googl.com> Reported-by: liujian <liujian56@huawei.com> Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Yuchung Cheng <ycheng@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-30tcp: Revert "tcp: remove header prediction"Florian Westphal1-0/+2
This reverts commit 45f119bf936b1f9f546a0b139c5b56f9bb2bdc78. Eric Dumazet says: We found at Google a significant regression caused by 45f119bf936b1f9f546a0b139c5b56f9bb2bdc78 tcp: remove header prediction In typical RPC (TCP_RR), when a TCP socket receives data, we now call tcp_ack() while we used to not call it. This touches enough cache lines to cause a slowdown. so problem does not seem to be HP removal itself but the tcp_ack() call. Therefore, it might be possible to remove HP after all, provided one finds a way to elide tcp_ack for most cases. Reported-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-10Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/netDavid S. Miller1-18/+9
The UDP offload conflict is dealt with by simply taking what is in net-next where we have removed all of the UFO handling code entirely. The TCP conflict was a case of local variables in a function being removed from both net and net-next. In netvsc we had an assignment right next to where a missing set of u64 stats sync object inits were added. Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-09tcp: fastopen: tcp_connect() must refresh the routeEric Dumazet1-0/+4
With new TCP_FASTOPEN_CONNECT socket option, there is a possibility to call tcp_connect() while socket sk_dst_cache is either NULL or invalid. +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4 +0 fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0 +0 setsockopt(4, SOL_TCP, TCP_FASTOPEN_CONNECT, [1], 4) = 0 +0 connect(4, ..., ...) = 0 << sk->sk_dst_cache becomes obsolete, or even set to NULL >> +1 sendto(4, ..., 1000, MSG_FASTOPEN, ..., ...) = 1000 We need to refresh the route otherwise bad things can happen, especially when syzkaller is running on the host :/ Fixes: 19f6d3f3c8422 ("net/tcp-fastopen: Add new API support") Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Wei Wang <weiwan@google.com> Cc: Yuchung Cheng <ycheng@google.com> Acked-by: Wei Wang <weiwan@google.com> Acked-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-04tcp: fix xmit timer to only be reset if data ACKed/SACKedNeal Cardwell1-9/+0
Fix a TCP loss recovery performance bug raised recently on the netdev list, in two threads: (i) July 26, 2017: netdev thread "TCP fast retransmit issues" (ii) July 26, 2017: netdev thread: "[PATCH V2 net-next] TLP: Don't reschedule PTO when there's one outstanding TLP retransmission" The basic problem is that incoming TCP packets that did not indicate forward progress could cause the xmit timer (TLP or RTO) to be rearmed and pushed back in time. In certain corner cases this could result in the following problems noted in these threads: - Repeated ACKs coming in with bogus SACKs corrupted by middleboxes could cause TCP to repeatedly schedule TLPs forever. We kept sending TLPs after every ~200ms, which elicited bogus SACKs, which caused more TLPs, ad infinitum; we never fired an RTO to fill in the holes. - Incoming data segments could, in some cases, cause us to reschedule our RTO or TLP timer further out in time, for no good reason. This could cause repeated inbound data to result in stalls in outbound data, in the presence of packet loss. This commit fixes these bugs by changing the TLP and RTO ACK processing to: (a) Only reschedule the xmit timer once per ACK. (b) Only reschedule the xmit timer if tcp_clean_rtx_queue() deems the ACK indicates sufficient forward progress (a packet was cumulatively ACKed, or we got a SACK for a packet that was sent before the most recent retransmit of the write queue head). This brings us back into closer compliance with the RFCs, since, as the comment for tcp_rearm_rto() notes, we should only restart the RTO timer after forward progress on the connection. Previously we were restarting the xmit timer even in these cases where there was no forward progress. As a side benefit, this commit simplifies and speeds up the TCP timer arming logic. We had been calling inet_csk_reset_xmit_timer() three times on normal ACKs that cumulatively acknowledged some data: 1) Once near the top of tcp_ack() to switch from TLP timer to RTO: if (icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) tcp_rearm_rto(sk); 2) Once in tcp_clean_rtx_queue(), to update the RTO: if (flag & FLAG_ACKED) { tcp_rearm_rto(sk); 3) Once in tcp_ack() after tcp_fastretrans_alert() to switch from RTO to TLP: if (icsk->icsk_pending == ICSK_TIME_RETRANS) tcp_schedule_loss_probe(sk); This commit, by only rescheduling the xmit timer once per ACK, simplifies the code and reduces CPU overhead. This commit was tested in an A/B test with Google web server traffic. SNMP stats and request latency metrics were within noise levels, substantiating that for normal web traffic patterns this is a rare issue. This commit was also tested with packetdrill tests to verify that it fixes the timer behavior in the corner cases discussed in the netdev threads mentioned above. This patch is a bug fix patch intended to be queued for -stable relases. Fixes: 6ba8a3b19e76 ("tcp: Tail loss probe (TLP)") Reported-by: Klavs Klavsen <kl@vsen.dk> Reported-by: Mao Wenan <maowenan@huawei.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Nandita Dukkipati <nanditad@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-04tcp: enable xmit timer fix by having TLP use time when RTO should fireNeal Cardwell1-9/+5
Have tcp_schedule_loss_probe() base the TLP scheduling decision based on when the RTO *should* fire. This is to enable the upcoming xmit timer fix in this series, where tcp_schedule_loss_probe() cannot assume that the last timer installed was an RTO timer (because we are no longer doing the "rearm RTO, rearm RTO, rearm TLP" dance on every ACK). So tcp_schedule_loss_probe() must independently figure out when an RTO would want to fire. In the new TLP implementation following in this series, we cannot assume that icsk_timeout was set based on an RTO; after processing a cumulative ACK the icsk_timeout we see can be from a previous TLP or RTO. So we need to independently recalculate the RTO time (instead of reading it out of icsk_timeout). Removing this dependency on the nature of icsk_timeout makes things a little easier to reason about anyway. Note that the old and new code should be equivalent, since they are both saying: "if the RTO is in the future, but at an earlier time than the normal TLP time, then set the TLP timer to fire when the RTO would have fired". Fixes: 6ba8a3b19e76 ("tcp: Tail loss probe (TLP)") Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Nandita Dukkipati <nanditad@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-01Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/netDavid S. Miller1-2/+3
Two minor conflicts in virtio_net driver (bug fix overlapping addition of a helper) and MAINTAINERS (new driver edit overlapping revamp of PHY entry). Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-01tcp: remove header predictionFlorian Westphal1-2/+0
Like prequeue, I am not sure this is overly useful nowadays. If we receive a train of packets, GRO will aggregate them if the headers are the same (HP predates GRO by several years) so we don't get a per-packet benefit, only a per-aggregated-packet one. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
2017-07-30tcp: avoid bogus gcc-7 array-bounds warningArnd Bergmann1-2/+3
When using CONFIG_UBSAN_SANITIZE_ALL, the TCP code produces a false-positive warning: net/ipv4/tcp_output.c: In function 'tcp_connect': net/ipv4/tcp_output.c:2207:40: error: array subscript is below array bounds [-Werror=array-bounds] tp->chrono_stat[tp->chrono_type - 1] += now - tp->chrono_start; ^~ net/ipv4/tcp_output.c:2207:40: error: array subscript is below array bounds [-Werror=array-bounds] tp->chrono_stat[tp->chrono_type - 1] += now - tp->chrono_start; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~ I have opened a gcc bug for this, but distros have already shipped compilers with this problem, and it's not clear yet whether there is a way for gcc to avoid the warning. As the problem is related to the bitfield access, this introduces a temporary variable to store the old enum value. I did not notice this warning earlier, since UBSAN is disabled when building with COMPILE_TEST, and that was always turned on in both allmodconfig and randconfig tests. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81601 Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: David S. Miller <davem@davemloft.net>
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