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

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

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/net/packetdrill/tcp_nagle_sendmsg_msg_more.pkt
Extension
.pkt
Size
2658 bytes
Lines
67
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 the MSG_MORE flag will correctly corks the tiny writes
`./defaults.sh`

    0 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 32792 <mss 1000,nop,wscale 7>
   +0 > S. 0:0(0) ack 1 <mss 1460,nop,wscale 8>
 +.01 < . 1:1(0) ack 1 win 257
   +0 accept(3, ..., ...) = 4
// Disable Nagle by default on this socket.
   +0 setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0

// Test the basic case: MSG_MORE overwrites TCP_NODELAY and enables Nagle.
   +0 sendmsg(4, {msg_name(...)=...,
                  msg_iov(1)=[{..., 40}], msg_flags=0}, MSG_MORE) = 40
 +.21~+.215 > P. 1:41(40) ack 1
 +.01 < . 1:1(0) ack 41 win 257

// Test unsetting MSG_MORE releases the packet
   +0 sendmsg(4, {msg_name(...)=...,
                  msg_iov(1)=[{..., 100}], msg_flags=0}, MSG_MORE) = 100
+.005 sendmsg(4, {msg_name(...)=...,
                  msg_iov(1)=[{..., 160}], msg_flags=0}, MSG_MORE) = 160
 +.01 sendmsg(4, {msg_name(...)=...,
                  msg_iov(3)=[{..., 100}, {..., 200}, {..., 195}],
		  msg_flags=0}, MSG_MORE) = 495
+.008 sendmsg(4, {msg_name(...)=...,
                  msg_iov(1)=[{..., 5}], msg_flags=0}, 0) = 5
   +0 > P. 41:801(760) ack 1
 +.02 < . 1:1(0) ack 801 win 257


// Test >MSS write will unleash MSS packets but hold on the remaining data.
  +.1 sendmsg(4, {msg_name(...)=...,
                  msg_iov(1)=[{..., 3100}], msg_flags=0}, MSG_MORE) = 3100
   +0 > . 801:3801(3000) ack 1
+.003 sendmsg(4, {msg_name(...)=...,
                  msg_iov(1)=[{..., 50}], msg_flags=0}, MSG_MORE) = 50

 +.01 < . 1:1(0) ack 2801 win 257
// Err... we relase the remaining right after the ACK? note that PUSH is reset
   +0 > . 3801:3951(150) ack 1

// Test we'll hold on the subsequent writes when inflight (3801:3951) > 0
+.001 sendmsg(4, {msg_name(...)=...,
                  msg_iov(1)=[{..., 1}], msg_flags=0}, MSG_MORE) = 1
+.002 sendmsg(4, {msg_name(...)=...,
                  msg_iov(1)=[{..., 2}], msg_flags=0}, MSG_MORE) = 2
+.003 sendmsg(4, {msg_name(...)=...,
                  msg_iov(1)=[{..., 3}], msg_flags=0}, MSG_MORE) = 3
+.004 sendmsg(4, {msg_name(...)=...,
                  msg_iov(1)=[{..., 4}], msg_flags=0}, MSG_MORE) = 4
 +.02 < . 1:1(0) ack 3951 win 257
   +0 > . 3951:3961(10) ack 1
 +.02 < . 1:1(0) ack 3961 win 257


// Test the case a MSG_MORE send followed by a write flushes the data
   +0 sendmsg(4, {msg_name(...)=...,
                  msg_iov(1)=[{..., 20}], msg_flags=0}, MSG_MORE) = 20
 +.05 write(4, ..., 20) = 20
   +0 > P. 3961:4001(40) ack 1

Annotation

Implementation Notes