tools/testing/selftests/net/packetdrill/tcp_tcp_info_tcp-info-sndbuf-limited.pkt

Source file repositories/reference/linux-study-clean/tools/testing/selftests/net/packetdrill/tcp_tcp_info_tcp-info-sndbuf-limited.pkt

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/net/packetdrill/tcp_tcp_info_tcp-info-sndbuf-limited.pkt
Extension
.pkt
Size
1589 bytes
Lines
39
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 send-buffer-limited time in tcp_info for client side.
`./defaults.sh`

// Create a socket and set it to non-blocking.
    0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
   +0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR)
   +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0

   +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
   +0 > S 0:0(0) <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8>
 +.01 < S. 0:0(0) ack 1 win 10000 <mss 1000,sackOK,nop,nop,nop,wscale 8>
   +0 > . 1:1(0) ack 1
   +0 getsockopt(3, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
   +0 fcntl(3, F_SETFL, O_RDWR) = 0   // set back to blocking
   +0 setsockopt(3, SOL_SOCKET, SO_SNDBUF, [10000], 4) = 0
   +0 getsockopt(3, SOL_SOCKET, SO_SNDBUF, [20000], [4]) = 0

 +.09...0.14 write(3, ..., 150000) = 150000

 +.01 < . 1:1(0) ack 10001 win 10000

 +.01 < . 1:1(0) ack 30001 win 10000

// cwnd goes from 40(60KB) to 80(120KB), and that we hit the tiny sndbuf limit 10KB
 +.01 < . 1:1(0) ack 70001 win 10000

 +.02 < . 1:1(0) ack 95001 win 10000
   +0 %{ assert 19000 <= tcpi_sndbuf_limited <= 21000, tcpi_sndbuf_limited; \
	 assert 49000 <= tcpi_busy_time <= 52000, tcpi_busy_time; \
	 assert 0 == tcpi_rwnd_limited, tcpi_rwnd_limited }%

// This ack frees up enough buffer so we are no longer
// buffer limited (socket flag SOCK_NOSPACE is cleared)
 +.02 < . 1:1(0) ack 150001 win 10000
   +0 %{ assert 19000 <= tcpi_sndbuf_limited <= 21000, tcpi_sndbuf_limited;\
	 assert 69000 <= tcpi_busy_time <= 73000, tcpi_busy_time;\
	 assert 0 == tcpi_rwnd_limited, tcpi_rwnd_limited }%

Annotation

Implementation Notes