tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0
2//
3// Send an ICMP host_unreachable pkt to a pending SYN_RECV req.
4//
5// If it's a TFO req, the ICMP error will cause it to switch
6// to TCP_CLOSE state but remains in the acceptor queue.
7
8--ip_version=ipv4
9
10`./defaults.sh`
11
12 0 socket(..., SOCK_STREAM|SOCK_NONBLOCK, IPPROTO_TCP) = 3
13 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
14 +0 bind(3, ..., ...) = 0
15 +0 listen(3, 1) = 0
16 +0 setsockopt(3, SOL_TCP, TCP_FASTOPEN, [1], 4) = 0
17
18 +0 < S 0:10(10) win 32792 <mss 1460,sackOK,nop,nop,FO TFO_COOKIE,nop,nop>
19 +0 > S. 0:0(0) ack 11 <mss 1460,nop,nop,sackOK>
20
21// Out-of-window icmp is ignored but accounted.
22 +0 `nstat > /dev/null`
23 +0 < icmp unreachable [5000:6000(1000)]
24 +0 `nstat | grep TcpExtOutOfWindowIcmps > /dev/null`
25
26// Valid ICMP unreach.
27 +0 < icmp unreachable host_unreachable [0:10(10)]
28
29// Unlike the non-TFO case, the req is still there to be accepted.
30 +0 accept(3, ..., ...) = 4
31 +0 %{ assert (tcpi_options & TCPI_OPT_SYN_DATA) != 0, tcpi_options }%
32
33// tcp_done_with_error() in tcp_v4_err() sets sk->sk_state
34// to TCP_CLOSE
35 +0 %{ assert tcpi_state == TCP_CLOSE, tcpi_state }%
36
37// The 1st read will succeed and return the data in SYN
38 +0 read(4, ..., 512) = 10
39
40// The 2nd read will fail.
41 +0 read(4, ..., 512) = -1 EHOSTUNREACH (No route to host)
42
43// But is no longer writable because it's in TCP_CLOSE state.
44 +0 write(4, ..., 100) = -1 EPIPE (Broken Pipe)
45
46// inbound pkt will trigger RST because the socket has been moved
47// off the TCP hash tables.
48 +0 < . 1:1(0) ack 1 win 32792
49 +0 > R 1:1(0)