tools/testing/selftests/net/packetdrill/tcp_syncookies_ip6_9k.pkt

Source file repositories/reference/linux-study-clean/tools/testing/selftests/net/packetdrill/tcp_syncookies_ip6_9k.pkt

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/net/packetdrill/tcp_syncookies_ip6_9k.pkt
Extension
.pkt
Size
1356 bytes
Lines
37
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: tools
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
//
// Check syncookies.
//
// Check we are able to rebuild client sack, wscale, ecn and mss options.
// IPv6 msstab[4] = { 1280 - 60, 1480 - 60, 1500 - 60, 9000 - 60 }

--ip_version=ipv6

`./defaults.sh
sysctl -q net.ipv4.tcp_syncookies=2
ip link set dev tun0 mtu 9000
`

    0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
   +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
   +0 bind(3, ..., ...) = 0
   +0 listen(3, 10) = 0

   +0 < S 0:0(0) win 32792 <mss 8940,sackOK,TS val 100 ecr 0,nop,wscale 10>
   +0 > S. 0:0(0) ack 1 <mss 8940,sackOK,TS val 4000 ecr 100,nop,wscale 8>
 +.01 < . 1:1(0) ack 1 win 1024 <nop,nop,TS val 110 ecr 4000>

   +0 accept(3, ..., ...) = 4

// Check we properly infer from the final packet the other peer wanted mss >= 8940, wscale 10, sackOK and no ECN.
// This is only possible because TCP TS option was used.
// Linux uses the SYNACK TS.val 6 low order bits to encode the options.

   +0 %{ assert tcpi_snd_mss == 8940 - 12, tcpi_snd_mss; \
         assert tcpi_snd_wscale == 10, tcpi_snd_wscale; \
         assert (tcpi_options & TCPI_OPT_SACK) != 0, tcpi_options; \
         assert (tcpi_options & TCPI_OPT_TIMESTAMPS) != 0, tcpi_options; \
         assert (tcpi_options & TCPI_OPT_WSCALE) != 0, tcpi_options; \
         assert (tcpi_options & TCPI_OPT_ECN) == 0, tcpi_options
}%

Annotation

Implementation Notes