tools/testing/selftests/net/packetdrill/tcp_sack_sack-shift-sacked-7-3-4-8-9-fack.pkt

Source file repositories/reference/linux-study-clean/tools/testing/selftests/net/packetdrill/tcp_sack_sack-shift-sacked-7-3-4-8-9-fack.pkt

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/net/packetdrill/tcp_sack_sack-shift-sacked-7-3-4-8-9-fack.pkt
Extension
.pkt
Size
2287 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 shifting of newly-SACKed ranges onto the previous already-SACKed skb.
// This variant tests the case where we mark packets 0-4 lost, then
// get a SACK for 3, and then a SACK for 4.

`./defaults.sh`

// Establish a connection and send 10 MSS.
    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,sackOK,nop,nop,nop,wscale 7>
   +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
  +.1 < . 1:1(0) ack 1 win 1024
   +0 accept(3, ..., ...) = 4

   +0 write(4, ..., 10000) = 10000
   +0 > P. 1:10001(10000) ack 1

// SACK for 7001:8001. Using RACK we delay the fast retransmit.
  +.1 < . 1:1(0) ack 1 win 257 <sack 7001:8001,nop,nop>
// RACK reordering timer
+.027 > . 1:1001(1000) ack 1
   +0 %{
assert tcpi_ca_state == TCP_CA_Recovery, tcpi_ca_state
assert tcpi_lost == 7, tcpi_lost  # RACK thinks 1:7001 are lost
assert tcpi_reordering == 3, tcpi_reordering
}%

// SACK for 3001:4001.
+.002 < . 1:1(0) ack 1 win 257 <sack 3001:4001 7001:8001,nop,nop>
   +0 > . 1001:2001(1000) ack 1
   +0 %{
assert tcpi_lost == 6, tcpi_lost              # since 3001:4001 is no longer lost
assert tcpi_reordering == 5, tcpi_reordering  # 7001:8001 -> 3001:4001
}%

// SACK for 4001:5001.
// This SACK for an adjacent range causes the sender to
// shift the newly-SACKed range onto the previous skb.
// It uses the RFC3517 algorithm to mark 1:3001 lost
// because >=3 higher-sequence packets are SACKed.
+.002 < . 1:1(0) ack 1 win 257 <sack 3001:5001 7001:8001,nop,nop>
   +0 > . 2001:3001(1000) ack 1
   +0 %{
assert tcpi_lost == 5,tcpi_lost         # SACK/RFC3517 thinks 1:3001 are lost
}%

// SACK for 8001:9001.
+.002 < . 1:1(0) ack 1 win 257 <sack 3001:5001 7001:9001,nop,nop>

// SACK for 9001:10001.
+.002 < . 1:1(0) ack 1 win 257 <sack 3001:5001 7001:10001,nop,nop>
   +0 > . 5001:6001(1000) ack 1

// To simplify clean-up, say we get an ACK for all data.
  +.1 < . 1:1(0) ack 10001 win 257
   +0 %{
assert tcpi_ca_state == TCP_CA_Open, tcpi_ca_state
assert tcpi_unacked == 0, tcpi_unacked
assert tcpi_sacked == 0, tcpi_sacked
assert tcpi_lost == 0, tcpi_lost
assert tcpi_retrans == 0, tcpi_retrans
}%

Annotation

Implementation Notes