selftests/net: packetdrill: add minimal client and server tests

Introduce minimal tests. These can serve as simple illustrative
examples, and as templates when writing new tests.

When adding new cases, it can be easier to extend an existing base
test rather than start from scratch. The existing tests all focus on
real, often non-trivial, features. It is not obvious which to take as
starting point, and arguably none really qualify.

Add two tests
- the client test performs the active open and initial close
- the server test implements the passive open and final close

Signed-off-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260105172529.3514786-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/tools/testing/selftests/net/packetdrill/tcp_basic_client.pkt b/tools/testing/selftests/net/packetdrill/tcp_basic_client.pkt
new file mode 100644 (file)
index 0000000..319f81d
--- /dev/null
+++ b/tools/testing/selftests/net/packetdrill/tcp_basic_client.pkt
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Minimal active open.
+// First to close connection.
+
+`./defaults.sh`
+
+    0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4
+
+   // Connect to server: active open: three-way handshake
+   +0...0 connect(4, ..., ...) = 0
+   +0 > S 0:0(0) <mss 1460,sackOK,TS val 0 ecr 0,nop,wscale 8>
+   +0 < S. 0:0(0) ack 1 win 65535 <mss 1460,sackOK,nop,nop,nop,wscale 7>
+   +0 > . 1:1(0) ack 1
+
+   // Send data
+   +0 send(4, ..., 1000, 0) = 1000
+   +0 > P. 1:1001(1000) ack 1
+   +0 < . 1:1(0) ack 1001 win 257
+
+   +0 close(4) = 0
+   +0 > F. 1001:1001(0) ack 1
+   +0 < F. 1:1(0) ack 1002 win 257
+   +0 > . 1002:1002(0) ack 2

diff --git a/tools/testing/selftests/net/packetdrill/tcp_basic_server.pkt b/tools/testing/selftests/net/packetdrill/tcp_basic_server.pkt
new file mode 100644 (file)
index 0000000..e72a291
--- /dev/null
+++ b/tools/testing/selftests/net/packetdrill/tcp_basic_server.pkt
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Minimal passive open.
+// Peer is first to close.
+
+`./defaults.sh`
+
+   // Open listener socket
+    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
+
+   // Incoming connection: passive open: three-way handshake
+   +0 < S 0:0(0) win 65535 <mss 1000,sackOK,nop,nop,nop,wscale 8>
+   +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
+   +0 < . 1:1(0) ack 1 win 257
+
+   // Open connection socket and close listener socket
+   +0 accept(3, ..., ...) = 4
+   +0 close(3) = 0
+
+   // Peer sends data: acknowledge and receive
+   +0 < P. 1:1001(1000) ack 1 win 257
+   +0 > . 1:1(0) ack 1001
+   +0 recv(4, ..., 1000, 0) = 1000
+
+   // Peer initiates connection close
+   +0 < F. 1001:1001(0) ack 1 win 257
+ +.04 > . 1:1(0) ack 1002
+
+   // Local socket also closes its side
+   +0 close(4) = 0
+   +0 > F. 1:1(0) ack 1002
+   +0 < . 1002:1002(0) ack 2 win 257