kernel/linux.git/net/ipv4/tcp_input.c, branch linux-4.13.y

tcp: fix tcp_fastretrans_alert warning

2017-11-24T07:35:56+00:00

[ Upstream commit 0eb96bf754d7fa6635aa0b0f6650c74b8a6b1cc9 ] This patch fixes the cause of an WARNING indicatng TCP has pending retransmission in Open state in tcp_fastretrans_alert(). The root cause is a bad interaction between path mtu probing, if enabled, and the RACK loss detection. Upong receiving a SACK above the sequence of the MTU probing packet, RACK could mark the probe packet lost in tcp_fastretrans_alert(), prior to calling tcp_simple_retransmit(). tcp_simple_retransmit() only enters Loss state if it newly marks the probe packet lost. If the probe packet is already identified as lost by RACK, the sender remains in Open state with some packets marked lost and retransmitted. Then the next SACK would trigger the warning. The likely scenario is that the probe packet was lost due to its size or network congestion. The actual impact of this warning is small by potentially entering fast recovery an ACK later. The simple fix is always entering recovery (Loss) state if some packet is marked lost during path MTU probing. Fixes: a0370b3f3f2c ("tcp: enable RACK loss detection to trigger recovery") Reported-by: Oleksandr Natalenko Reported-by: Alexei Starovoitov Reported-by: Roman Gushchin Signed-off-by: Yuchung Cheng Reviewed-by: Eric Dumazet Acked-by: Neal Cardwell Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

tcp/dccp: fix ireq->opt races

2017-11-18T10:30:36+00:00

[ Upstream commit c92e8c02fe664155ac4234516e32544bec0f113d ] syzkaller found another bug in DCCP/TCP stacks [1] For the reasons explained in commit ce1050089c96 ("tcp/dccp: fix ireq->pktopts race"), we need to make sure we do not access ireq->opt unless we own the request sock. Note the opt field is renamed to ireq_opt to ease grep games. [1] BUG: KASAN: use-after-free in ip_queue_xmit+0x1687/0x18e0 net/ipv4/ip_output.c:474 Read of size 1 at addr ffff8801c951039c by task syz-executor5/3295 CPU: 1 PID: 3295 Comm: syz-executor5 Not tainted 4.14.0-rc4+ #80 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:52 print_address_description+0x73/0x250 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report+0x25b/0x340 mm/kasan/report.c:409 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:427 ip_queue_xmit+0x1687/0x18e0 net/ipv4/ip_output.c:474 tcp_transmit_skb+0x1ab7/0x3840 net/ipv4/tcp_output.c:1135 tcp_send_ack.part.37+0x3bb/0x650 net/ipv4/tcp_output.c:3587 tcp_send_ack+0x49/0x60 net/ipv4/tcp_output.c:3557 __tcp_ack_snd_check+0x2c6/0x4b0 net/ipv4/tcp_input.c:5072 tcp_ack_snd_check net/ipv4/tcp_input.c:5085 [inline] tcp_rcv_state_process+0x2eff/0x4850 net/ipv4/tcp_input.c:6071 tcp_child_process+0x342/0x990 net/ipv4/tcp_minisocks.c:816 tcp_v4_rcv+0x1827/0x2f80 net/ipv4/tcp_ipv4.c:1682 ip_local_deliver_finish+0x2e2/0xba0 net/ipv4/ip_input.c:216 NF_HOOK include/linux/netfilter.h:249 [inline] ip_local_deliver+0x1ce/0x6e0 net/ipv4/ip_input.c:257 dst_input include/net/dst.h:464 [inline] ip_rcv_finish+0x887/0x19a0 net/ipv4/ip_input.c:397 NF_HOOK include/linux/netfilter.h:249 [inline] ip_rcv+0xc3f/0x1820 net/ipv4/ip_input.c:493 __netif_receive_skb_core+0x1a3e/0x34b0 net/core/dev.c:4476 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4514 netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4587 netif_receive_skb+0xae/0x390 net/core/dev.c:4611 tun_rx_batched.isra.50+0x5ed/0x860 drivers/net/tun.c:1372 tun_get_user+0x249c/0x36d0 drivers/net/tun.c:1766 tun_chr_write_iter+0xbf/0x160 drivers/net/tun.c:1792 call_write_iter include/linux/fs.h:1770 [inline] new_sync_write fs/read_write.c:468 [inline] __vfs_write+0x68a/0x970 fs/read_write.c:481 vfs_write+0x18f/0x510 fs/read_write.c:543 SYSC_write fs/read_write.c:588 [inline] SyS_write+0xef/0x220 fs/read_write.c:580 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x40c341 RSP: 002b:00007f469523ec10 EFLAGS: 00000293 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000718000 RCX: 000000000040c341 RDX: 0000000000000037 RSI: 0000000020004000 RDI: 0000000000000015 RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000 R10: 00000000000f4240 R11: 0000000000000293 R12: 00000000004b7fd1 R13: 00000000ffffffff R14: 0000000020000000 R15: 0000000000025000 Allocated by task 3295: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551 __do_kmalloc mm/slab.c:3725 [inline] __kmalloc+0x162/0x760 mm/slab.c:3734 kmalloc include/linux/slab.h:498 [inline] tcp_v4_save_options include/net/tcp.h:1962 [inline] tcp_v4_init_req+0x2d3/0x3e0 net/ipv4/tcp_ipv4.c:1271 tcp_conn_request+0xf6d/0x3410 net/ipv4/tcp_input.c:6283 tcp_v4_conn_request+0x157/0x210 net/ipv4/tcp_ipv4.c:1313 tcp_rcv_state_process+0x8ea/0x4850 net/ipv4/tcp_input.c:5857 tcp_v4_do_rcv+0x55c/0x7d0 net/ipv4/tcp_ipv4.c:1482 tcp_v4_rcv+0x2d10/0x2f80 net/ipv4/tcp_ipv4.c:1711 ip_local_deliver_finish+0x2e2/0xba0 net/ipv4/ip_input.c:216 NF_HOOK include/linux/netfilter.h:249 [inline] ip_local_deliver+0x1ce/0x6e0 net/ipv4/ip_input.c:257 dst_input include/net/dst.h:464 [inline] ip_rcv_finish+0x887/0x19a0 net/ipv4/ip_input.c:397 NF_HOOK include/linux/netfilter.h:249 [inline] ip_rcv+0xc3f/0x1820 net/ipv4/ip_input.c:493 __netif_receive_skb_core+0x1a3e/0x34b0 net/core/dev.c:4476 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4514 netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4587 netif_receive_skb+0xae/0x390 net/core/dev.c:4611 tun_rx_batched.isra.50+0x5ed/0x860 drivers/net/tun.c:1372 tun_get_user+0x249c/0x36d0 drivers/net/tun.c:1766 tun_chr_write_iter+0xbf/0x160 drivers/net/tun.c:1792 call_write_iter include/linux/fs.h:1770 [inline] new_sync_write fs/read_write.c:468 [inline] __vfs_write+0x68a/0x970 fs/read_write.c:481 vfs_write+0x18f/0x510 fs/read_write.c:543 SYSC_write fs/read_write.c:588 [inline] SyS_write+0xef/0x220 fs/read_write.c:580 entry_SYSCALL_64_fastpath+0x1f/0xbe Freed by task 3306: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3503 [inline] kfree+0xca/0x250 mm/slab.c:3820 inet_sock_destruct+0x59d/0x950 net/ipv4/af_inet.c:157 __sk_destruct+0xfd/0x910 net/core/sock.c:1560 sk_destruct+0x47/0x80 net/core/sock.c:1595 __sk_free+0x57/0x230 net/core/sock.c:1603 sk_free+0x2a/0x40 net/core/sock.c:1614 sock_put include/net/sock.h:1652 [inline] inet_csk_complete_hashdance+0xd5/0xf0 net/ipv4/inet_connection_sock.c:959 tcp_check_req+0xf4d/0x1620 net/ipv4/tcp_minisocks.c:765 tcp_v4_rcv+0x17f6/0x2f80 net/ipv4/tcp_ipv4.c:1675 ip_local_deliver_finish+0x2e2/0xba0 net/ipv4/ip_input.c:216 NF_HOOK include/linux/netfilter.h:249 [inline] ip_local_deliver+0x1ce/0x6e0 net/ipv4/ip_input.c:257 dst_input include/net/dst.h:464 [inline] ip_rcv_finish+0x887/0x19a0 net/ipv4/ip_input.c:397 NF_HOOK include/linux/netfilter.h:249 [inline] ip_rcv+0xc3f/0x1820 net/ipv4/ip_input.c:493 __netif_receive_skb_core+0x1a3e/0x34b0 net/core/dev.c:4476 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4514 netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4587 netif_receive_skb+0xae/0x390 net/core/dev.c:4611 tun_rx_batched.isra.50+0x5ed/0x860 drivers/net/tun.c:1372 tun_get_user+0x249c/0x36d0 drivers/net/tun.c:1766 tun_chr_write_iter+0xbf/0x160 drivers/net/tun.c:1792 call_write_iter include/linux/fs.h:1770 [inline] new_sync_write fs/read_write.c:468 [inline] __vfs_write+0x68a/0x970 fs/read_write.c:481 vfs_write+0x18f/0x510 fs/read_write.c:543 SYSC_write fs/read_write.c:588 [inline] SyS_write+0xef/0x220 fs/read_write.c:580 entry_SYSCALL_64_fastpath+0x1f/0xbe Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets") Fixes: 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table") Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

tcp: when rearming RTO, if RTO time is in past then fire RTO ASAP

2017-08-18T23:07:43+00:00

In some situations tcp_send_loss_probe() can realize that it's unable to send a loss probe (TLP), and falls back to calling tcp_rearm_rto() to schedule an RTO timer. In such cases, sometimes tcp_rearm_rto() realizes that the RTO was eligible to fire immediately or at some point in the past (delta_us <= 0). Previously in such cases tcp_rearm_rto() was scheduling such "overdue" RTOs to happen at now + icsk_rto, which caused needless delays of hundreds of milliseconds (and non-linear behavior that made reproducible testing difficult). This commit changes the logic to schedule "overdue" RTOs ASAP, rather than at now + icsk_rto. Fixes: 6ba8a3b19e76 ("tcp: Tail loss probe (TLP)") Suggested-by: Yuchung Cheng Signed-off-by: Neal Cardwell Signed-off-by: Yuchung Cheng Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: fix xmit timer to only be reset if data ACKed/SACKed

2017-08-03T22:38:31+00:00

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 Reported-by: Mao Wenan Signed-off-by: Neal Cardwell Signed-off-by: Yuchung Cheng Signed-off-by: Nandita Dukkipati Acked-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: introduce tcp_rto_delta_us() helper for xmit timer fix

2017-08-03T22:38:30+00:00

Pure refactor. This helper will be required in the xmit timer fix later in the patch series. (Because the TLP logic will want to make this calculation.) Fixes: 6ba8a3b19e76 ("tcp: Tail loss probe (TLP)") Signed-off-by: Neal Cardwell Signed-off-by: Yuchung Cheng Signed-off-by: Nandita Dukkipati Acked-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: avoid setting cwnd to invalid ssthresh after cwnd reduction states

2017-08-02T17:51:07+00:00

If the sender switches the congestion control during ECN-triggered cwnd-reduction state (CA_CWR), upon exiting recovery cwnd is set to the ssthresh value calculated by the previous congestion control. If the previous congestion control is BBR that always keep ssthresh to TCP_INIFINITE_SSTHRESH, cwnd ends up being infinite. The safe step is to avoid assigning invalid ssthresh value when recovery ends. Signed-off-by: Yuchung Cheng Signed-off-by: Neal Cardwell Acked-by: Eric Dumazet Signed-off-by: David S. Miller

bpf: Add support for changing congestion control

2017-07-01T23:15:14+00:00

Added support for changing congestion control for SOCK_OPS bpf programs through the setsockopt bpf helper function. It also adds a new SOCK_OPS op, BPF_SOCK_OPS_NEEDS_ECN, that is needed for congestion controls, like dctcp, that need to enable ECN in the SYN packets. Signed-off-by: Lawrence Brakmo Signed-off-by: David S. Miller

bpf: Add TCP connection BPF callbacks

2017-07-01T23:15:14+00:00

Added callbacks to BPF SOCK_OPS type program before an active connection is intialized and after a passive or active connection is established. The following patch demostrates how they can be used to set send and receive buffer sizes. Signed-off-by: Lawrence Brakmo Signed-off-by: David S. Miller

bpf: Support for per connection SYN/SYN-ACK RTOs

2017-07-01T23:15:13+00:00

This patch adds support for setting a per connection SYN and SYN_ACK RTOs from within a BPF_SOCK_OPS program. For example, to set small RTOs when it is known both hosts are within a datacenter. Signed-off-by: Lawrence Brakmo Signed-off-by: David S. Miller

tcp: Namespaceify sysctl_tcp_timestamps

2017-06-08T14:53:29+00:00

Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller