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2020-05-02tcp: cache line align MAX_TCP_HEADEREric Dumazet1-1/+1
[ Upstream commit 9bacd256f1354883d3c1402655153367982bba49 ] TCP stack is dumb in how it cooks its output packets. Depending on MAX_HEADER value, we might chose a bad ending point for the headers. If we align the end of TCP headers to cache line boundary, we make sure to always use the smallest number of cache lines, which always help. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Soheil Hassas Yeganeh <soheil@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>
2019-12-21tcp: Protect accesses to .ts_recent_stamp with {READ,WRITE}_ONCE()Guillaume Nault1-3/+3
[ Upstream commit 721c8dafad26ccfa90ff659ee19755e3377b829d ] Syncookies borrow the ->rx_opt.ts_recent_stamp field to store the timestamp of the last synflood. Protect them with READ_ONCE() and WRITE_ONCE() since reads and writes aren't serialised. Use of .rx_opt.ts_recent_stamp for storing the synflood timestamp was introduced by a0f82f64e269 ("syncookies: remove last_synq_overflow from struct tcp_sock"). But unprotected accesses were already there when timestamp was stored in .last_synq_overflow. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Guillaume Nault <gnault@redhat.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>
2019-12-21tcp: tighten acceptance of ACKs not matching a child socketGuillaume Nault1-1/+9
[ Upstream commit cb44a08f8647fd2e8db5cc9ac27cd8355fa392d8 ] When no synflood occurs, the synflood timestamp isn't updated. Therefore it can be so old that time_after32() can consider it to be in the future. That's a problem for tcp_synq_no_recent_overflow() as it may report that a recent overflow occurred while, in fact, it's just that jiffies has grown past 'last_overflow' + TCP_SYNCOOKIE_VALID + 2^31. Spurious detection of recent overflows lead to extra syncookie verification in cookie_v[46]_check(). At that point, the verification should fail and the packet dropped. But we should have dropped the packet earlier as we didn't even send a syncookie. Let's refine tcp_synq_no_recent_overflow() to report a recent overflow only if jiffies is within the [last_overflow, last_overflow + TCP_SYNCOOKIE_VALID] interval. This way, no spurious recent overflow is reported when jiffies wraps and 'last_overflow' becomes in the future from the point of view of time_after32(). However, if jiffies wraps and enters the [last_overflow, last_overflow + TCP_SYNCOOKIE_VALID] interval (with 'last_overflow' being a stale synflood timestamp), then tcp_synq_no_recent_overflow() still erroneously reports an overflow. In such cases, we have to rely on syncookie verification to drop the packet. We unfortunately have no way to differentiate between a fresh and a stale syncookie timestamp. In practice, using last_overflow as lower bound is problematic. If the synflood timestamp is concurrently updated between the time we read jiffies and the moment we store the timestamp in 'last_overflow', then 'now' becomes smaller than 'last_overflow' and tcp_synq_no_recent_overflow() returns true, potentially dropping a valid syncookie. Reading jiffies after loading the timestamp could fix the problem, but that'd require a memory barrier. Let's just accommodate for potential timestamp growth instead and extend the interval using 'last_overflow - HZ' as lower bound. Signed-off-by: Guillaume Nault <gnault@redhat.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>
2019-12-21tcp: fix rejected syncookies due to stale timestampsGuillaume Nault1-1/+1
[ Upstream commit 04d26e7b159a396372646a480f4caa166d1b6720 ] If no synflood happens for a long enough period of time, then the synflood timestamp isn't refreshed and jiffies can advance so much that time_after32() can't accurately compare them any more. Therefore, we can end up in a situation where time_after32(now, last_overflow + HZ) returns false, just because these two values are too far apart. In that case, the synflood timestamp isn't updated as it should be, which can trick tcp_synq_no_recent_overflow() into rejecting valid syncookies. For example, let's consider the following scenario on a system with HZ=1000: * The synflood timestamp is 0, either because that's the timestamp of the last synflood or, more commonly, because we're working with a freshly created socket. * We receive a new SYN, which triggers synflood protection. Let's say that this happens when jiffies == 2147484649 (that is, 'synflood timestamp' + HZ + 2^31 + 1). * Then tcp_synq_overflow() doesn't update the synflood timestamp, because time_after32(2147484649, 1000) returns false. With: - 2147484649: the value of jiffies, aka. 'now'. - 1000: the value of 'last_overflow' + HZ. * A bit later, we receive the ACK completing the 3WHS. But cookie_v[46]_check() rejects it because tcp_synq_no_recent_overflow() says that we're not under synflood. That's because time_after32(2147484649, 120000) returns false. With: - 2147484649: the value of jiffies, aka. 'now'. - 120000: the value of 'last_overflow' + TCP_SYNCOOKIE_VALID. Of course, in reality jiffies would have increased a bit, but this condition will last for the next 119 seconds, which is far enough to accommodate for jiffie's growth. Fix this by updating the overflow timestamp whenever jiffies isn't within the [last_overflow, last_overflow + HZ] range. That shouldn't have any performance impact since the update still happens at most once per second. Now we're guaranteed to have fresh timestamps while under synflood, so tcp_synq_no_recent_overflow() can safely use it with time_after32() in such situations. Stale timestamps can still make tcp_synq_no_recent_overflow() return the wrong verdict when not under synflood. This will be handled in the next patch. For 64 bits architectures, the problem was introduced with the conversion of ->tw_ts_recent_stamp to 32 bits integer by commit cca9bab1b72c ("tcp: use monotonic timestamps for PAWS"). The problem has always been there on 32 bits architectures. Fixes: cca9bab1b72c ("tcp: use monotonic timestamps for PAWS") Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Guillaume Nault <gnault@redhat.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>
2019-09-06tcp: fix tcp_rtx_queue_tail in case of empty retransmit queueTim Froidcoeur1-0/+4
Commit 8c3088f895a0 ("tcp: be more careful in tcp_fragment()") triggers following stack trace: [25244.848046] kernel BUG at ./include/linux/skbuff.h:1406! [25244.859335] RIP: 0010:skb_queue_prev+0x9/0xc [25244.888167] Call Trace: [25244.889182] <IRQ> [25244.890001] tcp_fragment+0x9c/0x2cf [25244.891295] tcp_write_xmit+0x68f/0x988 [25244.892732] __tcp_push_pending_frames+0x3b/0xa0 [25244.894347] tcp_data_snd_check+0x2a/0xc8 [25244.895775] tcp_rcv_established+0x2a8/0x30d [25244.897282] tcp_v4_do_rcv+0xb2/0x158 [25244.898666] tcp_v4_rcv+0x692/0x956 [25244.899959] ip_local_deliver_finish+0xeb/0x169 [25244.901547] __netif_receive_skb_core+0x51c/0x582 [25244.903193] ? inet_gro_receive+0x239/0x247 [25244.904756] netif_receive_skb_internal+0xab/0xc6 [25244.906395] napi_gro_receive+0x8a/0xc0 [25244.907760] receive_buf+0x9a1/0x9cd [25244.909160] ? load_balance+0x17a/0x7b7 [25244.910536] ? vring_unmap_one+0x18/0x61 [25244.911932] ? detach_buf+0x60/0xfa [25244.913234] virtnet_poll+0x128/0x1e1 [25244.914607] net_rx_action+0x12a/0x2b1 [25244.915953] __do_softirq+0x11c/0x26b [25244.917269] ? handle_irq_event+0x44/0x56 [25244.918695] irq_exit+0x61/0xa0 [25244.919947] do_IRQ+0x9d/0xbb [25244.921065] common_interrupt+0x85/0x85 [25244.922479] </IRQ> tcp_rtx_queue_tail() (called by tcp_fragment()) can call tcp_write_queue_prev() on the first packet in the queue, which will trigger the BUG in tcp_write_queue_prev(), because there is no previous packet. This happens when the retransmit queue is empty, for example in case of a zero window. Commit 8c3088f895a0 ("tcp: be more careful in tcp_fragment()") was not a simple cherry-pick of the original one from master (b617158dc096) because there is a specific TCP rtx queue only since v4.15. For more details, please see the commit message of b617158dc096 ("tcp: be more careful in tcp_fragment()"). The BUG() is hit due to the specific code added to versions older than v4.15. The comment in skb_queue_prev() (include/linux/skbuff.h:1406), just before the BUG_ON() somehow suggests to add a check before using it, what Tim did. In master, this code path causing the issue will not be taken because the implementation of tcp_rtx_queue_tail() is different: tcp_fragment() → tcp_rtx_queue_tail() → tcp_write_queue_prev() → skb_queue_prev() → BUG_ON() Fixes: 8c3088f895a0 ("tcp: be more careful in tcp_fragment()") Signed-off-by: Tim Froidcoeur <tim.froidcoeur@tessares.net> Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net> Reviewed-by: Christoph Paasch <cpaasch@apple.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
2019-08-11tcp: be more careful in tcp_fragment()Eric Dumazet1-0/+17
[ Upstream commit b617158dc096709d8600c53b6052144d12b89fab ] 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: Sasha Levin <sashal@kernel.org>
2019-08-04tcp: reset sk_send_head in tcp_write_queue_purgeSoheil Hassas Yeganeh1-5/+6
[ Upstream commit dbbf2d1e4077bab0c65ece2765d3fc69cf7d610f ] tcp_write_queue_purge clears all the SKBs in the write queue but does not reset the sk_send_head. As a result, we can have a NULL pointer dereference anywhere that we use tcp_send_head instead of the tcp_write_queue_tail. For example, after a27fd7a8ed38 (tcp: purge write queue upon RST), we can purge the write queue on RST. Prior to 75c119afe14f (tcp: implement rb-tree based retransmit queue), tcp_push will only check tcp_send_head and then accesses tcp_write_queue_tail to send the actual SKB. As a result, it will dereference a NULL pointer. This has been reported twice for 4.14 where we don't have 75c119afe14f: By Timofey Titovets: [ 422.081094] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038 [ 422.081254] IP: tcp_push+0x42/0x110 [ 422.081314] PGD 0 P4D 0 [ 422.081364] Oops: 0002 [#1] SMP PTI By Yongjian Xu: BUG: unable to handle kernel NULL pointer dereference at 0000000000000038 IP: tcp_push+0x48/0x120 PGD 80000007ff77b067 P4D 80000007ff77b067 PUD 7fd989067 PMD 0 Oops: 0002 [#18] SMP PTI Modules linked in: tcp_diag inet_diag tcp_bbr sch_fq iTCO_wdt iTCO_vendor_support pcspkr ixgbe mdio i2c_i801 lpc_ich joydev input_leds shpchp e1000e igb dca ptp pps_core hwmon mei_me mei ipmi_si ipmi_msghandler sg ses scsi_transport_sas enclosure ext4 jbd2 mbcache sd_mod ahci libahci megaraid_sas wmi ast ttm dm_mirror dm_region_hash dm_log dm_mod dax CPU: 6 PID: 14156 Comm: [ET_NET 6] Tainted: G D 4.14.26-1.el6.x86_64 #1 Hardware name: LENOVO ThinkServer RD440 /ThinkServer RD440, BIOS A0TS80A 09/22/2014 task: ffff8807d78d8140 task.stack: ffffc9000e944000 RIP: 0010:tcp_push+0x48/0x120 RSP: 0018:ffffc9000e947a88 EFLAGS: 00010246 RAX: 00000000000005b4 RBX: ffff880f7cce9c00 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000040 RDI: ffff8807d00f5000 RBP: ffffc9000e947aa8 R08: 0000000000001c84 R09: 0000000000000000 R10: ffff8807d00f5158 R11: 0000000000000000 R12: ffff8807d00f5000 R13: 0000000000000020 R14: 00000000000256d4 R15: 0000000000000000 FS: 00007f5916de9700(0000) GS:ffff88107fd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000038 CR3: 00000007f8226004 CR4: 00000000001606e0 Call Trace: tcp_sendmsg_locked+0x33d/0xe50 tcp_sendmsg+0x37/0x60 inet_sendmsg+0x39/0xc0 sock_sendmsg+0x49/0x60 sock_write_iter+0xb6/0x100 do_iter_readv_writev+0xec/0x130 ? rw_verify_area+0x49/0xb0 do_iter_write+0x97/0xd0 vfs_writev+0x7e/0xe0 ? __wake_up_common_lock+0x80/0xa0 ? __fget_light+0x2c/0x70 ? __do_page_fault+0x1e7/0x530 do_writev+0x60/0xf0 ? inet_shutdown+0xac/0x110 SyS_writev+0x10/0x20 do_syscall_64+0x6f/0x140 ? prepare_exit_to_usermode+0x8b/0xa0 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 RIP: 0033:0x3135ce0c57 RSP: 002b:00007f5916de4b00 EFLAGS: 00000293 ORIG_RAX: 0000000000000014 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000003135ce0c57 RDX: 0000000000000002 RSI: 00007f5916de4b90 RDI: 000000000000606f RBP: 0000000000000000 R08: 0000000000000000 R09: 00007f5916de8c38 R10: 0000000000000000 R11: 0000000000000293 R12: 00000000000464cc R13: 00007f5916de8c30 R14: 00007f58d8bef080 R15: 0000000000000002 Code: 48 8b 97 60 01 00 00 4c 8d 97 58 01 00 00 41 b9 00 00 00 00 41 89 f3 4c 39 d2 49 0f 44 d1 41 81 e3 00 80 00 00 0f 85 b0 00 00 00 <80> 4a 38 08 44 8b 8f 74 06 00 00 44 89 8f 7c 06 00 00 83 e6 01 RIP: tcp_push+0x48/0x120 RSP: ffffc9000e947a88 CR2: 0000000000000038 ---[ end trace 8d545c2e93515549 ]--- There is other scenario which found in stable 4.4: Allocated: [<ffffffff82f380a6>] __alloc_skb+0xe6/0x600 net/core/skbuff.c:218 [<ffffffff832466c3>] alloc_skb_fclone include/linux/skbuff.h:856 [inline] [<ffffffff832466c3>] sk_stream_alloc_skb+0xa3/0x5d0 net/ipv4/tcp.c:833 [<ffffffff83249164>] tcp_sendmsg+0xd34/0x2b00 net/ipv4/tcp.c:1178 [<ffffffff83300ef3>] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:755 Freed: [<ffffffff82f372fd>] __kfree_skb+0x1d/0x20 net/core/skbuff.c:676 [<ffffffff83288834>] sk_wmem_free_skb include/net/sock.h:1447 [inline] [<ffffffff83288834>] tcp_write_queue_purge include/net/tcp.h:1460 [inline] [<ffffffff83288834>] tcp_connect_init net/ipv4/tcp_output.c:3122 [inline] [<ffffffff83288834>] tcp_connect+0xb24/0x30c0 net/ipv4/tcp_output.c:3261 [<ffffffff8329b991>] tcp_v4_connect+0xf31/0x1890 net/ipv4/tcp_ipv4.c:246 BUG: KASAN: use-after-free in tcp_skb_pcount include/net/tcp.h:796 [inline] BUG: KASAN: use-after-free in tcp_init_tso_segs net/ipv4/tcp_output.c:1619 [inline] BUG: KASAN: use-after-free in tcp_write_xmit+0x3fc2/0x4cb0 net/ipv4/tcp_output.c:2056 [<ffffffff81515cd5>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408 [<ffffffff814f9784>] __asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:427 [<ffffffff83286582>] tcp_skb_pcount include/net/tcp.h:796 [inline] [<ffffffff83286582>] tcp_init_tso_segs net/ipv4/tcp_output.c:1619 [inline] [<ffffffff83286582>] tcp_write_xmit+0x3fc2/0x4cb0 net/ipv4/tcp_output.c:2056 [<ffffffff83287a40>] __tcp_push_pending_frames+0xa0/0x290 net/ipv4/tcp_output.c:2307 stable 4.4 and stable 4.9 don't have the commit abb4a8b870b5 ("tcp: purge write queue upon RST") which is referred in dbbf2d1e4077, in tcp_connect_init, it calls tcp_write_queue_purge, and does not reset sk_send_head, then UAF. stable 4.14 have the commit abb4a8b870b5 ("tcp: purge write queue upon RST"), in tcp_reset, it calls tcp_write_queue_purge(sk), and does not reset sk_send_head, then UAF. So this patch can be used to fix stable 4.4 and 4.9. Fixes: a27fd7a8ed38 (tcp: purge write queue upon RST) Reported-by: Timofey Titovets <nefelim4ag@gmail.com> Reported-by: Yongjian Xu <yongjianchn@gmail.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> Tested-by: Yongjian Xu <yongjianchn@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Mao Wenan <maowenan@huawei.com> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-06-17tcp: limit payload size of sacked skbsEric Dumazet1-0/+2
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>
2019-02-23tcp: clear icsk_backoff in tcp_write_queue_purge()Eric Dumazet1-0/+1
[ Upstream commit 04c03114be82194d4a4858d41dba8e286ad1787c ] soukjin bae reported a crash in tcp_v4_err() handling ICMP_DEST_UNREACH after tcp_write_queue_head(sk) returned a NULL pointer. Current logic should have prevented this : if (seq != tp->snd_una || !icsk->icsk_retransmits || !icsk->icsk_backoff || fastopen) break; Problem is the write queue might have been purged and icsk_backoff has not been cleared. Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: soukjin bae <soukjin.bae@samsung.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>
2018-10-13tcp: use an RB tree for ooo receive queueYaogong Wang1-1/+1
[ Upstream commit 9f5afeae51526b3ad7b7cb21ee8b145ce6ea7a7a ] Over the years, TCP BDP has increased by several orders of magnitude, and some people are considering to reach the 2 Gbytes limit. Even with current window scale limit of 14, ~1 Gbytes maps to ~740,000 MSS. In presence of packet losses (or reorders), TCP stores incoming packets into an out of order queue, and number of skbs sitting there waiting for the missing packets to be received can be in the 10^5 range. Most packets are appended to the tail of this queue, and when packets can finally be transferred to receive queue, we scan the queue from its head. However, in presence of heavy losses, we might have to find an arbitrary point in this queue, involving a linear scan for every incoming packet, throwing away cpu caches. This patch converts it to a RB tree, to get bounded latencies. Yaogong wrote a preliminary patch about 2 years ago. Eric did the rebase, added ofo_last_skb cache, polishing and tests. Tested with network dropping between 1 and 10 % packets, with good success (about 30 % increase of throughput in stress tests) Next step would be to also use an RB tree for the write queue at sender side ;) Signed-off-by: Yaogong Wang <wygivan@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Acked-By: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Mao Wenan <maowenan@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-08-24tcp: remove DELAYED ACK events in DCTCPYuchung Cheng1-2/+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>
2018-08-06tcp: add max_quickacks param to tcp_incr_quickack and tcp_enter_quickack_modeEric Dumazet1-1/+1
[ Upstream commit 9a9c9b51e54618861420093ae6e9b50a961914c5 ] We want to add finer control of the number of ACK packets sent after ECN events. This patch is not changing current behavior, it only enables following change. Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Soheil Hassas Yeganeh <soheil@google.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>
2018-07-28tcp: do not delay ACK in DCTCP upon CE status changeYuchung Cheng1-0/+1
[ Upstream commit a0496ef2c23b3b180902dd185d0d63ccbc624cf8 ] Per DCTCP RFC8257 (Section 3.2) the ACK reflecting the CE status change has to be sent immediately so the sender can respond quickly: """ When receiving packets, the CE codepoint MUST be processed as follows: 1. If the CE codepoint is set and DCTCP.CE is false, set DCTCP.CE to true and send an immediate ACK. 2. If the CE codepoint is not set and DCTCP.CE is true, set DCTCP.CE to false and send an immediate ACK. """ Previously DCTCP implementation may continue to delay the ACK. This patch fixes that to implement the RFC by forcing an immediate ACK. Tested with this packetdrill script provided by Larry Brakmo 0.000 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 0.000 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 0.000 setsockopt(3, SOL_TCP, TCP_CONGESTION, "dctcp", 5) = 0 0.000 bind(3, ..., ...) = 0 0.000 listen(3, 1) = 0 0.100 < [ect0] SEW 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7> 0.100 > SE. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8> 0.110 < [ect0] . 1:1(0) ack 1 win 257 0.200 accept(3, ..., ...) = 4 +0 setsockopt(4, SOL_SOCKET, SO_DEBUG, [1], 4) = 0 0.200 < [ect0] . 1:1001(1000) ack 1 win 257 0.200 > [ect01] . 1:1(0) ack 1001 0.200 write(4, ..., 1) = 1 0.200 > [ect01] P. 1:2(1) ack 1001 0.200 < [ect0] . 1001:2001(1000) ack 2 win 257 +0.005 < [ce] . 2001:3001(1000) ack 2 win 257 +0.000 > [ect01] . 2:2(0) ack 2001 // Previously the ACK below would be delayed by 40ms +0.000 > [ect01] E. 2:2(0) ack 3001 +0.500 < F. 9501:9501(0) ack 4 win 257 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: do not cancel delay-AcK on DCTCP special ACKYuchung Cheng1-0/+1
[ 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>
2018-03-22tcp: sysctl: Fix a race to avoid unexpected 0 window from spaceGao Feng1-3/+5
[ Upstream commit c48367427a39ea0b85c7cf018fe4256627abfd9e ] Because sysctl_tcp_adv_win_scale could be changed any time, so there is one race in tcp_win_from_space. For example, 1.sysctl_tcp_adv_win_scale<=0 (sysctl_tcp_adv_win_scale is negative now) 2.space>>(-sysctl_tcp_adv_win_scale) (sysctl_tcp_adv_win_scale is postive now) As a result, tcp_win_from_space returns 0. It is unexpected. Certainly if the compiler put the sysctl_tcp_adv_win_scale into one register firstly, then use the register directly, it would be ok. But we could not depend on the compiler behavior. Signed-off-by: Gao Feng <fgao@ikuai8.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>
2017-11-18tcp: fix tcp_mtu_probe() vs highest_sackEric Dumazet1-3/+3
[ Upstream commit 2b7cda9c35d3b940eb9ce74b30bbd5eb30db493d ] 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-11-21tcp: take care of truncations done by sk_filter()Eric Dumazet1-0/+1
[ Upstream commit ac6e780070e30e4c35bd395acfe9191e6268bdd3 ] With syzkaller help, Marco Grassi found a bug in TCP stack, crashing in tcp_collapse() Root cause is that sk_filter() can truncate the incoming skb, but TCP stack was not really expecting this to happen. It probably was expecting a simple DROP or ACCEPT behavior. We first need to make sure no part of TCP header could be removed. Then we need to adjust TCP_SKB_CB(skb)->end_seq Many thanks to syzkaller team and Marco for giving us a reproducer. Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Marco Grassi <marco.gra@gmail.com> Reported-by: Vladis Dronov <vdronov@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-09-30tcp: fix use after free in tcp_xmit_retransmit_queue()Eric Dumazet1-0/+2
[ Upstream commit bb1fceca22492109be12640d49f5ea5a544c6bb4 ] When tcp_sendmsg() allocates a fresh and empty skb, it puts it at the tail of the write queue using tcp_add_write_queue_tail() Then it attempts to copy user data into this fresh skb. If the copy fails, we undo the work and remove the fresh skb. Unfortunately, this undo lacks the change done to tp->highest_sack and we can leave a dangling pointer (to a freed skb) Later, tcp_xmit_retransmit_queue() can dereference this pointer and access freed memory. For regular kernels where memory is not unmapped, this might cause SACK bugs because tcp_highest_sack_seq() is buggy, returning garbage instead of tp->snd_nxt, but with various debug features like CONFIG_DEBUG_PAGEALLOC, this can crash the kernel. This bug was found by Marco Grassi thanks to syzkaller. Fixes: 6859d49475d4 ("[TCP]: Abstract tp->highest_sack accessing & point to next skb") Reported-by: Marco Grassi <marco.gra@gmail.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Cc: Yuchung Cheng <ycheng@google.com> Cc: Neal Cardwell <ncardwell@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
2016-03-04tcp: do not drop syn_recv on all icmp reportsEric Dumazet1-1/+1
[ Upstream commit 9cf7490360bf2c46a16b7525f899e4970c5fc144 ] Petr Novopashenniy reported that ICMP redirects on SYN_RECV sockets were leading to RST. This is of course incorrect. A specific list of ICMP messages should be able to drop a SYN_RECV. For instance, a REDIRECT on SYN_RECV shall be ignored, as we do not hold a dst per SYN_RECV pseudo request. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=111751 Fixes: 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table") Reported-by: Petr Novopashenniy <pety@rusnet.ru> 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>
2015-10-23tcp/dccp: fix hashdance race for passive sessionsEric Dumazet1-1/+3
Multiple cpus can process duplicates of incoming ACK messages matching a SYN_RECV request socket. This is a rare event under normal operations, but definitely can happen. Only one must win the race, otherwise corruption would occur. To fix this without adding new atomic ops, we use logic in inet_ehash_nolisten() to detect the request was present in the same ehash bucket where we try to insert the new child. If request socket was not found, we have to undo the child creation. This actually removes a spin_lock()/spin_unlock() pair in reqsk_queue_unlink() for the fast path. 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 <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-21tcp: use RACK to detect lossesYuchung Cheng1-0/+9
This patch implements the second half of RACK that uses the the most recent transmit time among all delivered packets to detect losses. tcp_rack_mark_lost() is called upon receiving a dubious ACK. It then checks if an not-yet-sacked packet was sent at least "reo_wnd" prior to the sent time of the most recently delivered. If so the packet is deemed lost. The "reo_wnd" reordering window starts with 1msec for fast loss detection and changes to min-RTT/4 when reordering is observed. We found 1msec accommodates well on tiny degree of reordering (<3 pkts) on faster links. We use min-RTT instead of SRTT because reordering is more of a path property but SRTT can be inflated by self-inflicated congestion. The factor of 4 is borrowed from the delayed early retransmit and seems to work reasonably well. Since RACK is still experimental, it is now used as a supplemental loss detection on top of existing algorithms. It is only effective after the fast recovery starts or after the timeout occurs. The fast recovery is still triggered by FACK and/or dupack threshold instead of RACK. We introduce a new sysctl net.ipv4.tcp_recovery for future experiments of loss recoveries. For now RACK can be disabled by setting it to 0. 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>
2015-10-21tcp: track the packet timings in RACKYuchung Cheng1-0/+5
This patch is the first half of the RACK loss recovery. RACK loss recovery uses the notion of time instead of packet sequence (FACK) or counts (dupthresh). It's inspired by the previous FACK heuristic in tcp_mark_lost_retrans(): when a limited transmit (new data packet) is sacked, then current retransmitted sequence below the newly sacked sequence must been lost, since at least one round trip time has elapsed. But it has several limitations: 1) can't detect tail drops since it depends on limited transmit 2) is disabled upon reordering (assumes no reordering) 3) only enabled in fast recovery ut not timeout recovery RACK (Recently ACK) addresses these limitations with the notion of time instead: a packet P1 is lost if a later packet P2 is s/acked, as at least one round trip has passed. Since RACK cares about the time sequence instead of the data sequence of packets, it can detect tail drops when later retransmission is s/acked while FACK or dupthresh can't. For reordering RACK uses a dynamically adjusted reordering window ("reo_wnd") to reduce false positives on ever (small) degree of reordering. This patch implements tcp_advanced_rack() which tracks the most recent transmission time among the packets that have been delivered (ACKed or SACKed) in tp->rack.mstamp. This timestamp is the key to determine which packet has been lost. Consider an example that the sender sends six packets: T1: P1 (lost) T2: P2 T3: P3 T4: P4 T100: sack of P2. rack.mstamp = T2 T101: retransmit P1 T102: sack of P2,P3,P4. rack.mstamp = T4 T205: ACK of P4 since the hole is repaired. rack.mstamp = T101 We need to be careful about spurious retransmission because it may falsely advance tp->rack.mstamp by an RTT or an RTO, causing RACK to falsely mark all packets lost, just like a spurious timeout. We identify spurious retransmission by the ACK's TS echo value. If TS option is not applicable but the retransmission is acknowledged less than min-RTT ago, it is likely to be spurious. We refrain from using the transmission time of these spurious retransmissions. The second half is implemented in the next patch that marks packet lost using RACK timestamp. 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>
2015-10-21tcp: track min RTT using windowed min-filterYuchung Cheng1-0/+7
Kathleen Nichols' algorithm for tracking the minimum RTT of a data stream over some measurement window. It uses constant space and constant time per update. Yet it almost always delivers the same minimum as an implementation that has to keep all the data in the window. The measurement window is tunable via sysctl.net.ipv4.tcp_min_rtt_wlen with a default value of 5 minutes. The algorithm keeps track of the best, 2nd best & 3rd best min values, maintaining an invariant that the measurement time of the n'th best >= n-1'th best. It also makes sure that the three values are widely separated in the time window since that bounds the worse case error when that data is monotonically increasing over the window. Upon getting a new min, we can forget everything earlier because it has no value - the new min is less than everything else in the window by definition and it's the most recent. So we restart fresh on every new min and overwrites the 2nd & 3rd choices. The same property holds for the 2nd & 3rd best. Therefore we have to maintain two invariants to maximize the information in the samples, one on values (1st.v <= 2nd.v <= 3rd.v) and the other on times (now-win <=1st.t <= 2nd.t <= 3rd.t <= now). These invariants determine the structure of the code The RTT input to the windowed filter is the minimum RTT measured from ACK or SACK, or as the last resort from TCP timestamps. The accessor tcp_min_rtt() returns the minimum RTT seen in the window. ~0U indicates it is not available. The minimum is 1usec even if the true RTT is below that. 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>
2015-10-19tcp: do not set queue_mapping on SYNACKEric Dumazet1-1/+1
At the time of commit fff326990789 ("tcp: reflect SYN queue_mapping into SYNACK packets") we had little ways to cope with SYN floods. We no longer need to reflect incoming skb queue mappings, and instead can pick a TX queue based on cpu cooking the SYNACK, with normal XPS affinities. Note that all SYNACK retransmits were picking TX queue 0, this no longer is a win given that SYNACK rtx are now distributed on all cpus. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-03tcp: attach SYNACK messages to request sockets instead of listenerEric Dumazet1-2/+4
If a listen backlog is very big (to avoid syncookies), then the listener sk->sk_wmem_alloc is the main source of false sharing, as we need to touch it twice per SYNACK re-transmit and TX completion. (One SYN packet takes listener lock once, but up to 6 SYNACK are generated) By attaching the skb to the request socket, we remove this source of contention. Tested: listen(fd, 10485760); // single listener (no SO_REUSEPORT) 16 RX/TX queue NIC Sustain a SYNFLOOD attack of ~320,000 SYN per second, Sending ~1,400,000 SYNACK per second. Perf profiles now show listener spinlock being next bottleneck. 20.29% [kernel] [k] queued_spin_lock_slowpath 10.06% [kernel] [k] __inet_lookup_established 5.12% [kernel] [k] reqsk_timer_handler 3.22% [kernel] [k] get_next_timer_interrupt 3.00% [kernel] [k] tcp_make_synack 2.77% [kernel] [k] ipt_do_table 2.70% [kernel] [k] run_timer_softirq 2.50% [kernel] [k] ip_finish_output 2.04% [kernel] [k] cascade Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-03tcp/dccp: install syn_recv requests into ehash tableEric Dumazet1-3/+0
In this patch, we insert request sockets into TCP/DCCP regular ehash table (where ESTABLISHED and TIMEWAIT sockets are) instead of using the per listener hash table. ACK packets find SYN_RECV pseudo sockets without having to find and lock the listener. In nominal conditions, this halves pressure on listener lock. Note that this will allow for SO_REUSEPORT refinements, so that we can select a listener using cpu/numa affinities instead of the prior 'consistent hash', since only SYN packets will apply this selection logic. We will shrink listen_sock in the following patch to ease code review. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Ying Cai <ycai@google.com> Cc: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-10-03tcp: get_openreq[46]() changesEric Dumazet1-1/+0
When request sockets are no longer in a per listener hash table but on regular TCP ehash, we need to access listener uid through req->rsk_listener get_openreq6() also gets a const for its request socket argument. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-30tcp: constify tcp_v{4|6}_route_req() sock argumentEric Dumazet1-1/+1
These functions do not change the listener socket. Goal is to make sure tcp_conn_request() is not messing with listener in a racy way. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-30tcp: cookie_init_sequence() cleanupsEric Dumazet1-9/+10
Some common IPv4/IPv6 code can be factorized. Also constify cookie_init_sequence() socket argument. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-30tcp/dccp: constify syn_recv_sock() method sock argumentEric Dumazet1-1/+1
We'll soon no longer hold listener socket lock, these functions do not modify the socket in any way. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-30tcp: constify tcp_create_openreq_child() socket argumentEric Dumazet1-1/+1
This method does not touch the listener socket. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-30tcp: remove tcp_rcv_state_process() tcp_hdr argumentEric Dumazet1-2/+1
Factorize code to get tcp header from skb. It makes no sense to duplicate code in callers. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-30tcp: remove unused len argument from tcp_rcv_state_process()Eric Dumazet1-1/+1
Once we realize tcp_rcv_synsent_state_process() does not use its 'len' argument and we get rid of it, then it becomes clear this argument is no longer used in tcp_rcv_state_process() Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-29tcp: avoid reorders for TFO passive connectionsEric Dumazet1-4/+4
We found that a TCP Fast Open passive connection was vulnerable to reorders, as the exchange might look like [1] C -> S S <FO ...> <request> [2] S -> C S. ack request <options> [3] S -> C . <answer> packets [2] and [3] can be generated at almost the same time. If C receives the 3rd packet before the 2nd, it will drop it as the socket is in SYN_SENT state and expects a SYNACK. S will have to retransmit the answer. Current OOO avoidance in linux is defeated because SYNACK packets are attached to the LISTEN socket, while DATA packets are attached to the children. They might be sent by different cpus, and different TX queues might be selected. It turns out that for TFO, we created a child, which is a full blown socket in TCP_SYN_RECV state, and we simply can attach the SYNACK packet to this socket. This means that at the time tcp_sendmsg() pushes DATA packet, skb->ooo_okay will be set iff the SYNACK packet had been sent and TX completed. This removes the reorder source at the host level. We also removed the export of tcp_try_fastopen(), as it is no longer called from IPv6. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-25tcp/dccp: constify rtx_synack() and friendsEric Dumazet1-1/+1
This is done to make sure we do not change listener socket while sending SYNACK packets while socket lock is not held. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-25tcp: constify tcp_v{4|6}_send_synack() socket argumentEric Dumazet1-1/+1
This documents fact that listener lock might not be held at the time SYNACK are sent. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-25tcp: constify tcp_make_synack() socket argumentEric Dumazet1-1/+1
listener socket is not locked when tcp_make_synack() is called. We better make sure no field is written. There is one exception : Since SYNACK packets are attached to the listener at this moment (or SYN_RECV child in case of Fast Open), sock_wmalloc() needs to update sk->sk_wmem_alloc, but this is done using atomic operations so this is safe. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-25tcp: md5: constify tcp_md5_do_lookup() socket argumentEric Dumazet1-5/+5
When TCP new listener is done, these functions will be called without socket lock being held. Make sure they don't change anything. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-25tcp: constify tcp_openreq_init_rwin()Eric Dumazet1-1/+2
Soon, listener socket wont be locked when tcp_openreq_init_rwin() is called. We need to read socket fields once, as their value could change under us. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-25tcp: constify listener socket in tcp_v[46]_init_req()Eric Dumazet1-1/+2
Soon, listener socket spinlock will no longer be held, add const arguments to tcp_v[46]_init_req() to make clear these functions can not mess socket fields. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-22tcp: usec resolution SYN/ACK RTTYuchung Cheng1-0/+1
Currently SYN/ACK RTT is measured in jiffies. For LAN the SYN/ACK RTT is often measured as 0ms or sometimes 1ms, which would affect RTT estimation and min RTT samping used by some congestion control. This patch improves SYN/ACK RTT to be usec resolution if platform supports it. While the timestamping of SYN/ACK is done in request sock, the RTT measurement is carefully arranged to avoid storing another u64 timestamp in tcp_sock. For regular handshake w/o SYNACK retransmission, the RTT is sampled right after the child socket is created and right before the request sock is released (tcp_check_req() in tcp_minisocks.c) For Fast Open the child socket is already created when SYN/ACK was sent, the RTT is sampled in tcp_rcv_state_process() after processing the final ACK an right before the request socket is released. If the SYN/ACK was retransmistted or SYN-cookie was used, we rely on TCP timestamps to measure the RTT. The sample is taken at the same place in tcp_rcv_state_process() after the timestamp values are validated in tcp_validate_incoming(). Note that we do not store TS echo value in request_sock for SYN-cookies, because the value is already stored in tp->rx_opt used by tcp_ack_update_rtt(). One side benefit is that the RTT measurement now happens before initializing congestion control (of the passive side). Therefore the congestion control can use the SYN/ACK RTT. 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>
2015-08-31tcp: use dctcp if enabled on the route to the initiatorDaniel Borkmann1-1/+1
Currently, the following case doesn't use DCTCP, even if it should: A responder has f.e. Cubic as system wide default, but for a specific route to the initiating host, DCTCP is being set in RTAX_CC_ALGO. The initiating host then uses DCTCP as congestion control, but since the initiator sets ECT(0), tcp_ecn_create_request() doesn't set ecn_ok, and we have to fall back to Reno after 3WHS completes. We were thinking on how to solve this in a minimal, non-intrusive way without bloating tcp_ecn_create_request() needlessly: lets cache the CA ecn option flag in RTAX_FEATURES. In other words, when ECT(0) is set on the SYN packet, set ecn_ok=1 iff route RTAX_FEATURES contains the unexposed (internal-only) DST_FEATURE_ECN_CA. This allows to only do a single metric feature lookup inside tcp_ecn_create_request(). Joint work with Florian Westphal. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-08-25tcp: refine pacing rate determinationEric Dumazet1-0/+2
When TCP pacing was added back in linux-3.12, we chose to apply a fixed ratio of 200 % against current rate, to allow probing for optimal throughput even during slow start phase, where cwnd can be doubled every other gRTT. At Google, we found it was better applying a different ratio while in Congestion Avoidance phase. This ratio was set to 120 %. We've used the normal tcp_in_slow_start() helper for a while, then tuned the condition to select the conservative ratio as soon as cwnd >= ssthresh/2 : - After cwnd reduction, it is safer to ramp up more slowly, as we approach optimal cwnd. - Initial ramp up (ssthresh == INFINITY) still allows doubling cwnd every other RTT. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Yuchung Cheng <ycheng@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-08-25tcp: fix slow start after idle vs TSO/GSOEric Dumazet1-0/+13
slow start after idle might reduce cwnd, but we perform this after first packet was cooked and sent. With TSO/GSO, it means that we might send a full TSO packet even if cwnd should have been reduced to IW10. Moving the SSAI check in skb_entail() makes sense, because we slightly reduce number of times this check is done, especially for large send() and TCP Small queue callbacks from softirq context. As Neal pointed out, we also need to perform the check if/when receive window opens. Tested: Following packetdrill test demonstrates the problem // Test of slow start after idle `sysctl -q net.ipv4.tcp_slow_start_after_idle=1` 0.000 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 < S 0:0(0) win 65535 <mss 1000,sackOK,nop,nop,nop,wscale 7> +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 6> +.100 < . 1:1(0) ack 1 win 511 +0 accept(3, ..., ...) = 4 +0 setsockopt(4, SOL_SOCKET, SO_SNDBUF, [200000], 4) = 0 +0 write(4, ..., 26000) = 26000 +0 > . 1:5001(5000) ack 1 +0 > . 5001:10001(5000) ack 1 +0 %{ assert tcpi_snd_cwnd == 10 }% +.100 < . 1:1(0) ack 10001 win 511 +0 %{ assert tcpi_snd_cwnd == 20, tcpi_snd_cwnd }% +0 > . 10001:20001(10000) ack 1 +0 > P. 20001:26001(6000) ack 1 +.100 < . 1:1(0) ack 26001 win 511 +0 %{ assert tcpi_snd_cwnd == 36, tcpi_snd_cwnd }% +4 write(4, ..., 20000) = 20000 // If slow start after idle works properly, we should send 5 MSS here (cwnd/2) +0 > . 26001:31001(5000) ack 1 +0 %{ assert tcpi_snd_cwnd == 10, tcpi_snd_cwnd }% +0 > . 31001:36001(5000) ack 1 Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Yuchung Cheng <ycheng@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-07-10tcp: do not slow start when cwnd equals ssthreshYuchung Cheng1-1/+1
In the original design slow start is only used to raise cwnd when cwnd is stricly below ssthresh. It makes little sense to slow start when cwnd == ssthresh: especially when hystart has set ssthresh in the initial ramp, or after recovery when cwnd resets to ssthresh. Not doing so will also help reduce the buffer bloat slightly. 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: Nandita Dukkipati <nanditad@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-07-10tcp: add tcp_in_slow_start helperYuchung Cheng1-1/+6
Add a helper to test the slow start condition in various congestion control modules and other places. This is to prepare a slight improvement in policy as to exactly when to slow start. 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: Nandita Dukkipati <nanditad@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-06-12tcp: fill shinfo->gso_size at last momentEric Dumazet1-5/+8
In commit cd7d8498c9a5 ("tcp: change tcp_skb_pcount() location") we stored gso_segs in a temporary cache hot location. This patch does the same for gso_size. This allows to save 2 cache line misses in tcp xmit path for the last packet that is considered but not sent because of various conditions (cwnd, tso defer, receiver window, TSQ...) Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-06-08tcp: get_cookie_sock() consolidationEric Dumazet1-0/+3
IPv4 and IPv6 share same implementation of get_cookie_sock(), and there is no point inlining it. We add tcp_ prefix to the common helper name and export it. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-05-19tcp: add rfc3168, section 6.1.1.1. fallbackDaniel Borkmann1-0/+2
This work as a follow-up of commit f7b3bec6f516 ("net: allow setting ecn via routing table") and adds RFC3168 section 6.1.1.1. fallback for outgoing ECN connections. In other words, this work adds a retry with a non-ECN setup SYN packet, as suggested from the RFC on the first timeout: [...] A host that receives no reply to an ECN-setup SYN within the normal SYN retransmission timeout interval MAY resend the SYN and any subsequent SYN retransmissions with CWR and ECE cleared. [...] Schematic client-side view when assuming the server is in tcp_ecn=2 mode, that is, Linux default since 2009 via commit 255cac91c3c9 ("tcp: extend ECN sysctl to allow server-side only ECN"): 1) Normal ECN-capable path: SYN ECE CWR -----> <----- SYN ACK ECE ACK -----> 2) Path with broken middlebox, when client has fallback: SYN ECE CWR ----X crappy middlebox drops packet (timeout, rtx) SYN -----> <----- SYN ACK ACK -----> In case we would not have the fallback implemented, the middlebox drop point would basically end up as: SYN ECE CWR ----X crappy middlebox drops packet (timeout, rtx) SYN ECE CWR ----X crappy middlebox drops packet (timeout, rtx) SYN ECE CWR ----X crappy middlebox drops packet (timeout, rtx) In any case, it's rather a smaller percentage of sites where there would occur such additional setup latency: it was found in end of 2014 that ~56% of IPv4 and 65% of IPv6 servers of Alexa 1 million list would negotiate ECN (aka tcp_ecn=2 default), 0.42% of these webservers will fail to connect when trying to negotiate with ECN (tcp_ecn=1) due to timeouts, which the fallback would mitigate with a slight latency trade-off. Recent related paper on this topic: Brian Trammell, Mirja Kühlewind, Damiano Boppart, Iain Learmonth, Gorry Fairhurst, and Richard Scheffenegger: "Enabling Internet-Wide Deployment of Explicit Congestion Notification." Proc. PAM 2015, New York. http://ecn.ethz.ch/ecn-pam15.pdf Thus, when net.ipv4.tcp_ecn=1 is being set, the patch will perform RFC3168, section 6.1.1.1. fallback on timeout. For users explicitly not wanting this which can be in DC use case, we add a net.ipv4.tcp_ecn_fallback knob that allows for disabling the fallback. tp->ecn_flags are not being cleared in tcp_ecn_clear_syn() on output, but rather we let tcp_ecn_rcv_synack() take that over on input path in case a SYN ACK ECE was delayed. Thus a spurious SYN retransmission will not prevent ECN being negotiated eventually in that case. Reference: https://www.ietf.org/proceedings/92/slides/slides-92-iccrg-1.pdf Reference: https://www.ietf.org/proceedings/89/slides/slides-89-tsvarea-1.pdf Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Mirja Kühlewind <mirja.kuehlewind@tik.ee.ethz.ch> Signed-off-by: Brian Trammell <trammell@tik.ee.ethz.ch> Cc: Eric Dumazet <edumazet@google.com> Cc: Dave That <dave.taht@gmail.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-05-18tcp: introduce tcp_under_memory_pressure()Eric Dumazet1-0/+8
Introduce an optimized version of sk_under_memory_pressure() for TCP. Our intent is to use it in fast paths. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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