strace/tests/sock_filter-v.c

/*
 * Check decoding of socket filters.
 *
 * Copyright (c) 2017 Dmitry V. Levin <ldv@altlinux.org>
 * Copyright (c) 2017-2018 The strace developers.
 * All rights reserved.
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "tests.h"

#include <stdio.h>
#include <unistd.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <linux/filter.h>

/* SO_GET_FILTER was introduced by Linux commit v3.8-rc1~139^2~518 */
#ifndef SO_GET_FILTER
# define SO_GET_FILTER SO_ATTACH_FILTER
#endif

#define HEX_FMT "%#x"

#if XLAT_RAW
# define XLAT_FMT HEX_FMT
# define XLAT_ARGS(a_) (a_)
#elif XLAT_VERBOSE
# define XLAT_FMT HEX_FMT " /* %s */"
# define XLAT_ARGS(a_) (a_), #a_
#else
# define XLAT_FMT "%s"
# define XLAT_ARGS(a_) #a_
#endif

#define PRINT_STMT(pfx, code_fmt, k_fmt, ...)	\
	printf("%sBPF_STMT(" code_fmt ", " k_fmt ")", pfx, __VA_ARGS__)

#define PRINT_JUMP(pfx, code_fmt, k, jt, jf, ...)		\
	printf("%sBPF_JUMP(" code_fmt ", %#x, %#x, %#x)",	\
	       pfx, __VA_ARGS__, k, jt, jf)

static const struct sock_filter bpf_filter[] = {
	BPF_STMT(BPF_LD|BPF_B|BPF_ABS, SKF_LL_OFF+4),
	BPF_STMT(BPF_LD|BPF_B|BPF_ABS, SKF_NET_OFF+8),
	BPF_STMT(BPF_LD|BPF_B|BPF_ABS, SKF_AD_OFF+SKF_AD_PROTOCOL),
	BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, IPPROTO_UDP, 0, 5),
	BPF_STMT(BPF_LD|BPF_W|BPF_LEN, 0),
	BPF_JUMP(BPF_JMP|BPF_K|BPF_JGE, 100, 0, 3),
	BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 42),
	BPF_JUMP(BPF_JMP|BPF_K|BPF_JEQ, 'a', 0, 1),
	BPF_STMT(BPF_RET|BPF_K, -1U),
	BPF_STMT(BPF_RET|BPF_K, 0)
};

static void
print_filter(void)
{
	PRINT_STMT("[", XLAT_FMT "|" XLAT_FMT "|" XLAT_FMT,
		   XLAT_FMT "+4",
		   XLAT_ARGS(BPF_LD), XLAT_ARGS(BPF_B), XLAT_ARGS(BPF_ABS),
		   XLAT_ARGS(SKF_LL_OFF));
	PRINT_STMT(", ", XLAT_FMT "|" XLAT_FMT "|" XLAT_FMT,
		   XLAT_FMT "+8",
		   XLAT_ARGS(BPF_LD), XLAT_ARGS(BPF_B), XLAT_ARGS(BPF_ABS),
		   XLAT_ARGS(SKF_NET_OFF));
	PRINT_STMT(", ", XLAT_FMT "|" XLAT_FMT "|" XLAT_FMT,
		   XLAT_FMT "+" XLAT_FMT,
		   XLAT_ARGS(BPF_LD), XLAT_ARGS(BPF_B), XLAT_ARGS(BPF_ABS),
		   XLAT_ARGS(SKF_AD_OFF), XLAT_ARGS(SKF_AD_PROTOCOL));
	PRINT_JUMP(", ", XLAT_FMT "|" XLAT_FMT "|" XLAT_FMT,
		   IPPROTO_UDP, 0, 5,
		   XLAT_ARGS(BPF_JMP), XLAT_ARGS(BPF_K), XLAT_ARGS(BPF_JEQ));
	PRINT_STMT(", ", XLAT_FMT "|" XLAT_FMT "|" XLAT_FMT,
		   HEX_FMT,
		   XLAT_ARGS(BPF_LD), XLAT_ARGS(BPF_W), XLAT_ARGS(BPF_LEN),
		   0);
	PRINT_JUMP(", ", XLAT_FMT "|" XLAT_FMT "|" XLAT_FMT,
		   100, 0, 3,
		   XLAT_ARGS(BPF_JMP), XLAT_ARGS(BPF_K), XLAT_ARGS(BPF_JGE));
	PRINT_STMT(", ", XLAT_FMT "|" XLAT_FMT "|" XLAT_FMT,
		   HEX_FMT,
		   XLAT_ARGS(BPF_LD), XLAT_ARGS(BPF_B), XLAT_ARGS(BPF_ABS),
		   42);
	PRINT_JUMP(", ", XLAT_FMT "|" XLAT_FMT "|" XLAT_FMT,
		   'a', 0, 1,
		   XLAT_ARGS(BPF_JMP), XLAT_ARGS(BPF_K), XLAT_ARGS(BPF_JEQ));
	PRINT_STMT(", ", XLAT_FMT "|" XLAT_FMT,
		   HEX_FMT,
		   XLAT_ARGS(BPF_RET), XLAT_ARGS(BPF_K),
		   -1U);
	PRINT_STMT(", ", XLAT_FMT "|" XLAT_FMT,
		   HEX_FMT,
		   XLAT_ARGS(BPF_RET), XLAT_ARGS(BPF_K),
		   0);
	putchar(']');
}

static const char *errstr;

static int
get_filter(int fd, void *val, socklen_t *len)
{
	int rc = getsockopt(fd, SOL_SOCKET, SO_GET_FILTER, val, len);
	errstr = sprintrc(rc);
	return rc;
}

static int
set_filter(int fd, void *val, socklen_t len)
{
	int rc = setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, val, len);
	errstr = sprintrc(rc);
	return rc;
}

int
main(void)
{
	int rc;
	struct sock_filter *const filter =
		tail_memdup(bpf_filter, sizeof(bpf_filter));
	void *const efault = filter + ARRAY_SIZE(bpf_filter);
	TAIL_ALLOC_OBJECT_CONST_PTR(struct sock_fprog, prog);
	TAIL_ALLOC_OBJECT_CONST_PTR(socklen_t, len);

	prog->len = ARRAY_SIZE(bpf_filter);
	prog->filter = filter;

	int fd = socket(AF_INET, SOCK_DGRAM, 0);
	if (fd < 0)
		perror_msg_and_skip("socket AF_INET SOCK_DGRAM");

	/* query sock_filter program length -> 0 */
	*len = BPF_MAXINSNS;
	rc = get_filter(fd, NULL, len);
	if (rc)
		perror_msg_and_skip("getsockopt SOL_SOCKET SO_GET_FILTER");
	printf("getsockopt(%d, " XLAT_FMT ", " XLAT_FMT ", NULL, [%u->0]) "
	       "= 0\n",
	       fd, XLAT_ARGS(SOL_SOCKET), XLAT_ARGS(SO_GET_FILTER),
	       BPF_MAXINSNS);

	/* getsockopt NULL optlen - EFAULT */
	rc = get_filter(fd, NULL, NULL);
	printf("getsockopt(%d, " XLAT_FMT ", " XLAT_FMT ", NULL, NULL) "
	       "= %s\n",
	       fd, XLAT_ARGS(SOL_SOCKET), XLAT_ARGS(SO_GET_FILTER), errstr);

	/* attach a filter */
	rc = set_filter(fd, prog, sizeof(*prog));
	if (rc)
		perror_msg_and_skip("setsockopt SOL_SOCKET SO_ATTACH_FILTER");
	printf("setsockopt(%d, " XLAT_FMT ", " XLAT_FMT ", {len=%u, filter=",
	       fd, XLAT_ARGS(SOL_SOCKET), XLAT_ARGS(SO_ATTACH_FILTER),
	       prog->len);
	print_filter();
	printf("}, %u) = 0\n", (unsigned int) sizeof(*prog));

	/* setsockopt optlen is too small - EINVAL */
	rc = set_filter(fd, prog, sizeof(*prog) - 4);
	printf("setsockopt(%d, " XLAT_FMT ", " XLAT_FMT ", %p, %u) = %s\n",
	       fd, XLAT_ARGS(SOL_SOCKET), XLAT_ARGS(SO_ATTACH_FILTER), prog,
	       (unsigned int) sizeof(*prog) - 4, errstr);

#ifdef SO_ATTACH_REUSEPORT_CBPF
	rc = setsockopt(fd, SOL_SOCKET, SO_ATTACH_REUSEPORT_CBPF,
			prog, sizeof(*prog));
	errstr = sprintrc(rc);
	printf("setsockopt(%d, " XLAT_FMT ", " XLAT_FMT ", {len=%u, filter=",
	       fd, XLAT_ARGS(SOL_SOCKET), XLAT_ARGS(SO_ATTACH_REUSEPORT_CBPF),
	       prog->len);
	print_filter();
	printf("}, %u) = %s\n", (unsigned int) sizeof(*prog), errstr);
#endif

	/* query sock_filter program length -> ARRAY_SIZE(bpf_filter) */
	*len = 0;
	rc = get_filter(fd, efault, len);
	printf("getsockopt(%d, " XLAT_FMT ", " XLAT_FMT ", %p, [0->%u]) "
	       "= %s\n",
	       fd, XLAT_ARGS(SOL_SOCKET), XLAT_ARGS(SO_GET_FILTER), efault,
	       (unsigned int) ARRAY_SIZE(bpf_filter), errstr);

	/* getsockopt optlen is too small - EINVAL */
	*len = ARRAY_SIZE(bpf_filter) - 1;
	rc = get_filter(fd, efault, len);
	printf("getsockopt(%d, " XLAT_FMT ", " XLAT_FMT ", %p, [%u]) = %s\n",
	       fd, XLAT_ARGS(SOL_SOCKET), XLAT_ARGS(SO_GET_FILTER), efault,
	       (unsigned int) ARRAY_SIZE(bpf_filter) - 1, errstr);

	/* getsockopt optval EFAULT */
	*len = ARRAY_SIZE(bpf_filter);
	rc = get_filter(fd, filter + 1, len);
	printf("getsockopt(%d, " XLAT_FMT ", " XLAT_FMT ", %p, [%u]) = %s\n",
	       fd, XLAT_ARGS(SOL_SOCKET), XLAT_ARGS(SO_GET_FILTER),
	       filter + 1, (unsigned int) ARRAY_SIZE(bpf_filter), errstr);

	/* getsockopt optlen is too large - truncated */
	*len = ARRAY_SIZE(bpf_filter) + 1;
	rc = get_filter(fd, filter, len);
	printf("getsockopt(%d, " XLAT_FMT ", " XLAT_FMT ", ",
	       fd, XLAT_ARGS(SOL_SOCKET), XLAT_ARGS(SO_GET_FILTER));
	print_filter();
	printf(", [%u->%d]) = %s\n",
	       (unsigned int) ARRAY_SIZE(bpf_filter) + 1, *len, errstr);

	puts("+++ exited with 0 +++");
	return 0;
}