doc: Add test program verifying socket RST behaviour

Add a program to doc/platform-requirements testing / documenting the
RST related behaviour of TCP sockets under various conditions.

This doesn't fix bug 191 of itself, but documents the kernel side
behaviour we'll be using in order to fix it.

Link: https://bugs.passt.top/show_bug.cgi?id=191
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

3 files changed, 211 insertions, 2 deletions

diff --git a/doc/platform-requirements/.gitignore b/doc/platform-requirements/.gitignore
index f6272cf..b2a0069 100644
--- a/doc/platform-requirements/.gitignore
+++ b/doc/platform-requirements/.gitignore
@@ -1,4 +1,5 @@
 /listen-vs-repair
 /reuseaddr-priority
 /recv-zero
+/tcp-close-rst
 /udp-close-dup
diff --git a/doc/platform-requirements/Makefile b/doc/platform-requirements/Makefile
index 83930ef..204341b 100644
--- a/doc/platform-requirements/Makefile
+++ b/doc/platform-requirements/Makefile
@@ -3,8 +3,10 @@
 # Copyright Red Hat
 # Author: David Gibson <david@gibson.dropbear.id.au>
 
-TARGETS = reuseaddr-priority recv-zero udp-close-dup listen-vs-repair
-SRCS = reuseaddr-priority.c recv-zero.c udp-close-dup.c listen-vs-repair.c
+TARGETS = reuseaddr-priority recv-zero udp-close-dup listen-vs-repair \
+	tcp-close-rst
+SRCS = reuseaddr-priority.c recv-zero.c udp-close-dup.c listen-vs-repair.c \
+	tcp-close-rst.c
 CFLAGS = -Wall
 
 all: cppcheck clang-tidy $(TARGETS:%=check-%)
@@ -25,6 +27,7 @@ clang-tidy:
 	clang-tidy --checks=*,\
 	-altera-id-dependent-backward-branch,\
 	-altera-unroll-loops,\
+	-android-cloexec-accept,\
 	-bugprone-easily-swappable-parameters,\
 	-clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling,\
 	-concurrency-mt-unsafe,\
@@ -37,6 +40,7 @@ clang-tidy:
 	-misc-include-cleaner,\
 	-modernize-macro-to-enum,\
 	-readability-braces-around-statements,\
+	-readability-function-cognitive-complexity,\
 	-readability-identifier-length,\
 	-readability-isolate-declaration \
 	$(SRCS)
diff --git a/doc/platform-requirements/tcp-close-rst.c b/doc/platform-requirements/tcp-close-rst.c
new file mode 100644
index 0000000..0e508f6
--- /dev/null
+++ b/doc/platform-requirements/tcp-close-rst.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/* tcp-close-rst.c
+ *
+ * Check what operations on a TCP socket will trigger an RST.
+ *
+ * Copyright Red Hat
+ * Author: David Gibson <david@gibson.dropbear.id.au>
+ */
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <net/if.h>
+#include <netinet/in.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "common.h"
+
+#define DSTPORT	13258U
+
+#define SRCADDR(n) \
+	(0x7f000000U | (n) << 16U | (n) << 8U | 0x1U)
+
+#define BASENUM	100
+
+/* 127.0.0.1:DSTPORT */
+static const struct sockaddr_in lo_dst = SOCKADDR_INIT(INADDR_LOOPBACK, DSTPORT);
+
+#define	LINGER		0x01U
+#define	SHUT_CLIENT	0x02U
+#define SHUT_SERVER	0x04U
+
+#define NUM_OPTIONS	(SHUT_SERVER << 1U)
+
+static void client_close(int sl, unsigned flags)
+{
+	struct sockaddr_in src = SOCKADDR_INIT(SRCADDR(flags), 0);
+	struct linger linger0 = {
+		.l_onoff = 1,
+		.l_linger = 0,
+	};
+	int sockerr, sc, sa;
+	socklen_t errlen = sizeof(sockerr);
+
+	printf("Client close %u:%s%s%s\n", flags,
+	       flags & LINGER ? " LINGER" : "",
+	       flags & SHUT_CLIENT ? " SHUT_CLIENT" : "",
+	       flags & SHUT_SERVER ? " SHUT_SERVER" : "");
+
+	sc = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
+	if (sc < 0)
+		die("socket() for connect(): %s\n", strerror(errno));
+
+	if (bind(sc, (struct sockaddr *)&src, sizeof(src)) < 0)
+		die("bind() for connect: %s\n", strerror(errno));
+
+	if (connect(sc, (struct sockaddr *)&lo_dst, sizeof(lo_dst)) < 0)
+		die("connect(): %s\n", strerror(errno));
+
+	/* cppcheck-suppress [android-cloexec-accept,unmatchedSuppression] */
+	sa = accept(sl, NULL, NULL);
+	if (sa < 0)
+		die("accept(): %s\n", strerror(errno));
+
+	if (flags & SHUT_SERVER)
+		if (shutdown(sa, SHUT_WR) < 0)
+			die("shutdown() server: %s\n", strerror(errno));
+
+	if (flags & SHUT_CLIENT)
+		if (shutdown(sc, SHUT_WR) < 0)
+			die("shutdown() client: %s\n", strerror(errno));
+
+	if (flags & LINGER)
+		if (setsockopt(sc, SOL_SOCKET, SO_LINGER,
+			       &linger0, sizeof(linger0)) < 0)
+			die("SO_LINGER: %s\n", strerror(errno));
+
+	close(sc);
+
+	if (getsockopt(sa, SOL_SOCKET, SO_ERROR, &sockerr, &errlen) < 0)
+		die("SO_ERROR: %s\n", strerror(errno));
+
+	if (errlen != sizeof(sockerr))
+		die("SO_ERROR: bad option length\n");
+
+	printf("Server error: %s\n", strerror(sockerr));
+
+	if (flags & LINGER) {
+		if (!(flags & SHUT_SERVER) || !(flags & SHUT_CLIENT)) {
+			if (sockerr == 0)
+				die("No error after abrupt close(), no RST?\n");
+		} else {
+			if (sockerr != 0)
+				die("Error after full shutdown, bogus RST?\n");
+		}
+	}
+
+	close(sa);
+}
+
+static void server_close(int sl, unsigned flags)
+{
+	struct sockaddr_in src = SOCKADDR_INIT(SRCADDR(flags), 0);
+	struct linger linger0 = {
+		.l_onoff = 1,
+		.l_linger = 0,
+	};
+	int sockerr, sc, sa;
+	socklen_t errlen = sizeof(sockerr);
+
+	printf("Server close %u:%s%s%s\n", flags,
+	       flags & LINGER ? " LINGER" : "",
+	       flags & SHUT_CLIENT ? " SHUT_CLIENT" : "",
+	       flags & SHUT_SERVER ? " SHUT_SERVER" : "");
+
+	sc = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
+	if (sc < 0)
+		die("socket() for connect(): %s\n", strerror(errno));
+
+	if (bind(sc, (struct sockaddr *)&src, sizeof(src)) < 0)
+		die("bind() for connect: %s\n", strerror(errno));
+
+	if (connect(sc, (struct sockaddr *)&lo_dst, sizeof(lo_dst)) < 0)
+		die("connect(): %s\n", strerror(errno));
+
+	/* cppcheck-suppress [android-cloexec-accept,unmatchedSuppression] */
+	sa = accept(sl, NULL, NULL);
+	if (sa < 0)
+		die("accept(): %s\n", strerror(errno));
+
+	if (flags & SHUT_SERVER)
+		if (shutdown(sa, SHUT_WR) < 0)
+			die("shutdown() server: %s\n", strerror(errno));
+
+	if (flags & SHUT_CLIENT)
+		if (shutdown(sc, SHUT_WR) < 0)
+			die("shutdown() client: %s\n", strerror(errno));
+
+	if (flags & LINGER)
+		if (setsockopt(sa, SOL_SOCKET, SO_LINGER,
+			       &linger0, sizeof(linger0)) < 0)
+			die("SO_LINGER: %s\n", strerror(errno));
+
+	close(sa);
+
+	if (getsockopt(sc, SOL_SOCKET, SO_ERROR, &sockerr, &errlen) < 0)
+		die("SO_ERROR: %s\n", strerror(errno));
+
+	if (errlen != sizeof(sockerr))
+		die("SO_ERROR: bad option length\n");
+
+	printf("Client error: %s\n", strerror(sockerr));
+
+	if (flags & LINGER) {
+		if (!(flags & SHUT_SERVER) || !(flags & SHUT_CLIENT)) {
+			if (sockerr == 0)
+				die("No error after abrupt close(), no RST?\n");
+		} else {
+			if (sockerr != 0)
+				die("Error after full shutdown, bogus RST?\n");
+		}
+	}
+
+	close(sc);
+}
+
+int main(int argc, char *argv[])
+{
+	unsigned flags;
+	int y = 1;
+	int sl;
+
+	(void)argc;
+	(void)argv;
+
+	sl = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
+	if (sl < 0)
+		die("socket() for listen: %s\n", strerror(errno));
+
+	if (setsockopt(sl, SOL_SOCKET, SO_REUSEADDR, &y, sizeof(y)) < 0)
+		die("SO_REUSEADDR for listen: %s\n", strerror(errno));
+
+	if (bind(sl, (struct sockaddr *)&lo_dst, sizeof(lo_dst)) < 0)
+		die("bind() for listen: %s\n", strerror(errno));
+
+	if (listen(sl, 1) < 0)
+		die("listen(): %s\n", strerror(errno));
+
+	printf("Listening on port %u\n", DSTPORT);
+
+	for (flags = 0; flags < NUM_OPTIONS; flags++) {
+		client_close(sl, flags);
+		server_close(sl, flags);
+	}
+
+	close(sl);
+	exit(0);
+}