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

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

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/net/packetdrill/tcp_rcv_neg_window.pkt
Extension
.pkt
Size
1171 bytes
Lines
35
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
// Test maximum advertised window limit when rcv_nxt advances past
// rcv_mwnd_seq. The "usable window" must be properly clamped to zero
// rather than becoming negative.

--mss=1000

`./defaults.sh`

// Establish a connection.
   +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
   +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
   +0 setsockopt(3, SOL_SOCKET, SO_RCVBUF, [20000], 4) = 0
   +0 bind(3, ..., ...) = 0
   +0 listen(3, 1) = 0

   +0 < S 0:0(0) win 32792 <mss 1000,nop,wscale 7>
   +0 > S. 0:0(0) ack 1 win 18980 <mss 1460,nop,wscale 0>
  +.1 < . 1:1(0) ack 1 win 257

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

// A too big packet is accepted if the receive queue is empty. It
// does not trigger an immediate ACK.
   +0 < P. 1:20001(20000) ack 1 win 257
   +0 %{ assert tcpi_bytes_received == 20000, tcpi_bytes_received; }%

// Send a RST immediately so that there is no rcv_wup/rcv_mwnd_seq update yet
   +0 < R. 20001:20001(0) ack 1 win 257

// Verify that the RST was accepted. Indirectly this also verifies that no
// immediate ACK was sent for the data packet above.
   +0 < . 20001:20001(0) ack 1 win 257
   +0 > R 1:1(0)

Annotation

Implementation Notes