From ec2691a12ed4c25b6fe3f542f45d13a5ef52db67 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Fri, 5 Jul 2024 20:44:09 +1000 Subject: doc: Test behaviour of zero length datagram recv()s Add a test program verifying that we're able to discard datagrams from a socket without needing a big discard buffer, by using a zero length recv(). Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- doc/platform-requirements/.gitignore | 1 + doc/platform-requirements/Makefile | 6 +-- doc/platform-requirements/recv-zero.c | 74 +++++++++++++++++++++++++++++++++++ 3 files changed, 78 insertions(+), 3 deletions(-) create mode 100644 doc/platform-requirements/recv-zero.c diff --git a/doc/platform-requirements/.gitignore b/doc/platform-requirements/.gitignore index c1baa98..555031d 100644 --- a/doc/platform-requirements/.gitignore +++ b/doc/platform-requirements/.gitignore @@ -1 +1,2 @@ /reuseaddr-priority +/recv-zero diff --git a/doc/platform-requirements/Makefile b/doc/platform-requirements/Makefile index 6e1d966..82aaac2 100644 --- a/doc/platform-requirements/Makefile +++ b/doc/platform-requirements/Makefile @@ -3,8 +3,8 @@ # Copyright Red Hat # Author: David Gibson -TARGETS = reuseaddr-priority -SRCS = reuseaddr-priority.c +TARGETS = reuseaddr-priority recv-zero +SRCS = reuseaddr-priority.c recv-zero.c CFLAGS = -Wall all: cppcheck clang-tidy $(TARGETS:%=check-%) @@ -16,7 +16,7 @@ check-%: % cppcheck: cppcheck --std=c11 --error-exitcode=1 --enable=all --force \ - --check-level=exhaustive \ + --check-level=exhaustive --inline-suppr \ --inconclusive --library=posix --quiet \ --suppress=missingIncludeSystem \ $(SRCS) diff --git a/doc/platform-requirements/recv-zero.c b/doc/platform-requirements/recv-zero.c new file mode 100644 index 0000000..f161e5c --- /dev/null +++ b/doc/platform-requirements/recv-zero.c @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0-or-later + +/* recv-zero.c + * + * Verify that we're able to discard datagrams by recv()ing into a zero-length + * buffer. + * + * Copyright Red Hat + * Author: David Gibson + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "common.h" + +#define DSTPORT 13257U + +/* 127.0.0.1:DSTPORT */ +static const struct sockaddr_in lo_dst = SOCKADDR_INIT(INADDR_LOOPBACK, DSTPORT); + +static void test_discard(void) +{ + long token1, token2; + int recv_s, send_s; + ssize_t rc; + + token1 = random(); + token2 = random(); + + recv_s = sock_reuseaddr(); + if (bind(recv_s, (struct sockaddr *)&lo_dst, sizeof(lo_dst)) < 0) + die("bind(): %s\n", strerror(errno)); + + send_s = sock_reuseaddr(); + if (connect(send_s, (struct sockaddr *)&lo_dst, sizeof(lo_dst)) < 0) + die("connect(): %s\n", strerror(errno)); + + send_token(send_s, token1); + send_token(send_s, token2); + + /* cppcheck-suppress nullPointer */ + rc = recv(recv_s, NULL, 0, MSG_DONTWAIT); + if (rc < 0) + die("discarding recv(): %s\n", strerror(errno)); + + recv_token(recv_s, token2); + + /* cppcheck-suppress nullPointer */ + rc = recv(recv_s, NULL, 0, MSG_DONTWAIT); + if (rc < 0 && errno != EAGAIN) + die("redundant discarding recv(): %s\n", strerror(errno)); + if (rc >= 0) + die("Unexpected receive: rc=%zd\n", rc); +} + +int main(int argc, char *argv[]) +{ + (void)argc; + (void)argv; + + test_discard(); + + printf("Discarding datagrams with a 0-length recv() seems to work\n"); + + exit(0); +} -- cgit v1.2.3