selftests/bpf: Selftest for sys_connect hooks

Add selftest for BPF_CGROUP_INET4_CONNECT and BPF_CGROUP_INET6_CONNECT
attach types.

Try to connect(2) to specified IP:port and test that:
* remote IP:port pair is overridden;
* local end of connection is bound to specified IP.

All combinations of IPv4/IPv6 and TCP/UDP are tested.

Example:
# tcpdump -pn -i lo -w connect.pcap 2>/dev/null &
[1] 478
# strace -qqf -e connect -o connect.trace ./test_sock_addr.sh
Wait for testing IPv4/IPv6 to become available ... OK
Load bind4 with invalid type (can pollute stderr) ... REJECTED
Load bind4 with valid type ... OK
Attach bind4 with invalid type ... REJECTED
Attach bind4 with valid type ... OK
Load connect4 with invalid type (can pollute stderr) libbpf: load bpf \
program failed: Permission denied
libbpf: -- BEGIN DUMP LOG ---
libbpf:
0: (b7) r2 = 23569
1: (63) *(u32 *)(r1 +24) = r2
2: (b7) r2 = 16777343
3: (63) *(u32 *)(r1 +4) = r2
invalid bpf_context access off=4 size=4
[ 1518.404609] random: crng init done

libbpf: -- END LOG --
libbpf: failed to load program 'cgroup/connect4'
libbpf: failed to load object './connect4_prog.o'
... REJECTED
Load connect4 with valid type ... OK
Attach connect4 with invalid type ... REJECTED
Attach connect4 with valid type ... OK
Test case #1 (IPv4/TCP):
Requested: bind(192.168.1.254, 4040) ..
Actual: bind(127.0.0.1, 4444)
Requested: connect(192.168.1.254, 4040) from (*, *) ..
Actual: connect(127.0.0.1, 4444) from (127.0.0.4, 56068)
Test case #2 (IPv4/UDP):
Requested: bind(192.168.1.254, 4040) ..
Actual: bind(127.0.0.1, 4444)
Requested: connect(192.168.1.254, 4040) from (*, *) ..
Actual: connect(127.0.0.1, 4444) from (127.0.0.4, 56447)
Load bind6 with invalid type (can pollute stderr) ... REJECTED
Load bind6 with valid type ... OK
Attach bind6 with invalid type ... REJECTED
Attach bind6 with valid type ... OK
Load connect6 with invalid type (can pollute stderr) libbpf: load bpf \
program failed: Permission denied
libbpf: -- BEGIN DUMP LOG ---
libbpf:
0: (b7) r6 = 0
1: (63) *(u32 *)(r1 +12) = r6
invalid bpf_context access off=12 size=4

libbpf: -- END LOG --
libbpf: failed to load program 'cgroup/connect6'
libbpf: failed to load object './connect6_prog.o'
... REJECTED
Load connect6 with valid type ... OK
Attach connect6 with invalid type ... REJECTED
Attach connect6 with valid type ... OK
Test case #3 (IPv6/TCP):
Requested: bind(face:b00c:1234:5678::abcd, 6060) ..
Actual: bind(::1, 6666)
Requested: connect(face:b00c:1234:5678::abcd, 6060) from (*, *)
Actual: connect(::1, 6666) from (::6, 37458)
Test case #4 (IPv6/UDP):
Requested: bind(face:b00c:1234:5678::abcd, 6060) ..
Actual: bind(::1, 6666)
Requested: connect(face:b00c:1234:5678::abcd, 6060) from (*, *)
Actual: connect(::1, 6666) from (::6, 39315)
### SUCCESS
# egrep 'connect\(.*AF_INET' connect.trace | \
> egrep -vw 'htons\(1025\)' | fold -b -s -w 72
502 connect(7, {sa_family=AF_INET, sin_port=htons(4040),
sin_addr=inet_addr("192.168.1.254")}, 128) = 0
502 connect(8, {sa_family=AF_INET, sin_port=htons(4040),
sin_addr=inet_addr("192.168.1.254")}, 128) = 0
502 connect(9, {sa_family=AF_INET6, sin6_port=htons(6060),
inet_pton(AF_INET6, "face:b00c:1234:5678::abcd", &sin6_addr),
sin6_flowinfo=0, sin6_scope_id=0}, 128) = 0
502 connect(10, {sa_family=AF_INET6, sin6_port=htons(6060),
inet_pton(AF_INET6, "face:b00c:1234:5678::abcd", &sin6_addr),
sin6_flowinfo=0, sin6_scope_id=0}, 128) = 0
# fg
tcpdump -pn -i lo -w connect.pcap 2> /dev/null
# tcpdump -r connect.pcap -n tcp | cut -c 1-72
reading from file connect.pcap, link-type EN10MB (Ethernet)
17:57:40.383533 IP 127.0.0.4.56068 > 127.0.0.1.4444: Flags [S], seq 1333
17:57:40.383566 IP 127.0.0.1.4444 > 127.0.0.4.56068: Flags [S.], seq 112
17:57:40.383589 IP 127.0.0.4.56068 > 127.0.0.1.4444: Flags [.], ack 1, w
17:57:40.384578 IP 127.0.0.1.4444 > 127.0.0.4.56068: Flags [R.], seq 1,
17:57:40.403327 IP6 ::6.37458 > ::1.6666: Flags [S], seq 406513443, win
17:57:40.403357 IP6 ::1.6666 > ::6.37458: Flags [S.], seq 2448389240, ac
17:57:40.403376 IP6 ::6.37458 > ::1.6666: Flags [.], ack 1, win 342, opt
17:57:40.404263 IP6 ::1.6666 > ::6.37458: Flags [R.], seq 1, ack 1, win

Signed-off-by: Andrey Ignatov <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>

tools/include/uapi/linux/bpf.h

···
 	BPF_SK_MSG_VERDICT,
 	BPF_CGROUP_INET4_BIND,
 	BPF_CGROUP_INET6_BIND,
+	BPF_CGROUP_INET4_CONNECT,
+	BPF_CGROUP_INET6_CONNECT,
 	__MAX_BPF_ATTACH_TYPE
 };
 
···
  *     @flags: reserved for future use
  *     Return: SK_PASS
  *
+ * int bpf_bind(ctx, addr, addr_len)
+ *     Bind socket to address. Only binding to IP is supported, no port can be
+ *     set in addr.
+ *     @ctx: pointer to context of type bpf_sock_addr
+ *     @addr: pointer to struct sockaddr to bind socket to
+ *     @addr_len: length of sockaddr structure
+ *     Return: 0 on success or negative error code
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
···
 	FN(msg_redirect_map),		\
 	FN(msg_apply_bytes),		\
 	FN(msg_cork_bytes),		\
-	FN(msg_pull_data),
+	FN(msg_pull_data),		\
+	FN(bind),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call

tools/lib/bpf/libbpf.c

···
 	BPF_PROG_SEC("sk_msg",		BPF_PROG_TYPE_SK_MSG),
 	BPF_SA_PROG_SEC("cgroup/bind4",	BPF_CGROUP_INET4_BIND),
 	BPF_SA_PROG_SEC("cgroup/bind6",	BPF_CGROUP_INET6_BIND),
+	BPF_SA_PROG_SEC("cgroup/connect4", BPF_CGROUP_INET4_CONNECT),
+	BPF_SA_PROG_SEC("cgroup/connect6", BPF_CGROUP_INET6_CONNECT),
 };
 
 #undef BPF_PROG_SEC

tools/testing/selftests/bpf/Makefile

···
 	sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o test_tracepoint.o \
 	test_l4lb_noinline.o test_xdp_noinline.o test_stacktrace_map.o \
 	sample_map_ret0.o test_tcpbpf_kern.o test_stacktrace_build_id.o \
-	sockmap_tcp_msg_prog.o
+	sockmap_tcp_msg_prog.o connect4_prog.o connect6_prog.o
 
 # Order correspond to 'make run_tests' order
 TEST_PROGS := test_kmod.sh \
 	test_libbpf.sh \
 	test_xdp_redirect.sh \
 	test_xdp_meta.sh \
-	test_offload.py
+	test_offload.py \
+	test_sock_addr.sh
 
 # Compile but not part of 'make run_tests'
 TEST_GEN_PROGS_EXTENDED = test_libbpf_open

tools/testing/selftests/bpf/bpf_helpers.h

···
 	(void *) BPF_FUNC_msg_cork_bytes;
 static int (*bpf_msg_pull_data)(void *ctx, int start, int end, int flags) =
 	(void *) BPF_FUNC_msg_pull_data;
+static int (*bpf_bind)(void *ctx, void *addr, int addr_len) =
+	(void *) BPF_FUNC_bind;
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions

tools/testing/selftests/bpf/connect4_prog.c

···
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <string.h>
+
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+#include <linux/in.h>
+#include <linux/in6.h>
+#include <sys/socket.h>
+
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+
+#define SRC_REWRITE_IP4		0x7f000004U
+#define DST_REWRITE_IP4		0x7f000001U
+#define DST_REWRITE_PORT4	4444
+
+int _version SEC("version") = 1;
+
+SEC("cgroup/connect4")
+int connect_v4_prog(struct bpf_sock_addr *ctx)
+{
+	struct sockaddr_in sa;
+
+	/* Rewrite destination. */
+	ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);
+	ctx->user_port = bpf_htons(DST_REWRITE_PORT4);
+
+	if (ctx->type == SOCK_DGRAM || ctx->type == SOCK_STREAM) {
+		///* Rewrite source. */
+		memset(&sa, 0, sizeof(sa));
+
+		sa.sin_family = AF_INET;
+		sa.sin_port = bpf_htons(0);
+		sa.sin_addr.s_addr = bpf_htonl(SRC_REWRITE_IP4);
+
+		if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
+			return 0;
+	}
+
+	return 1;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/connect6_prog.c

···
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <string.h>
+
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+#include <linux/in.h>
+#include <linux/in6.h>
+#include <sys/socket.h>
+
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+
+#define SRC_REWRITE_IP6_0	0
+#define SRC_REWRITE_IP6_1	0
+#define SRC_REWRITE_IP6_2	0
+#define SRC_REWRITE_IP6_3	6
+
+#define DST_REWRITE_IP6_0	0
+#define DST_REWRITE_IP6_1	0
+#define DST_REWRITE_IP6_2	0
+#define DST_REWRITE_IP6_3	1
+
+#define DST_REWRITE_PORT6	6666
+
+int _version SEC("version") = 1;
+
+SEC("cgroup/connect6")
+int connect_v6_prog(struct bpf_sock_addr *ctx)
+{
+	struct sockaddr_in6 sa;
+
+	/* Rewrite destination. */
+	ctx->user_ip6[0] = bpf_htonl(DST_REWRITE_IP6_0);
+	ctx->user_ip6[1] = bpf_htonl(DST_REWRITE_IP6_1);
+	ctx->user_ip6[2] = bpf_htonl(DST_REWRITE_IP6_2);
+	ctx->user_ip6[3] = bpf_htonl(DST_REWRITE_IP6_3);
+
+	ctx->user_port = bpf_htons(DST_REWRITE_PORT6);
+
+	if (ctx->type == SOCK_DGRAM || ctx->type == SOCK_STREAM) {
+		/* Rewrite source. */
+		memset(&sa, 0, sizeof(sa));
+
+		sa.sin6_family = AF_INET6;
+		sa.sin6_port = bpf_htons(0);
+
+		sa.sin6_addr.s6_addr32[0] = bpf_htonl(SRC_REWRITE_IP6_0);
+		sa.sin6_addr.s6_addr32[1] = bpf_htonl(SRC_REWRITE_IP6_1);
+		sa.sin6_addr.s6_addr32[2] = bpf_htonl(SRC_REWRITE_IP6_2);
+		sa.sin6_addr.s6_addr32[3] = bpf_htonl(SRC_REWRITE_IP6_3);
+
+		if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
+			return 0;
+	}
+
+	return 1;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/test_sock_addr.c

···
 #include <linux/filter.h>
 
 #include <bpf/bpf.h>
+#include <bpf/libbpf.h>
 
 #include "cgroup_helpers.h"
 
 #define CG_PATH	"/foo"
+#define CONNECT4_PROG_PATH	"./connect4_prog.o"
+#define CONNECT6_PROG_PATH	"./connect6_prog.o"
 
 #define SERV4_IP		"192.168.1.254"
 #define SERV4_REWRITE_IP	"127.0.0.1"
···
 			  sizeof(insns) / sizeof(struct bpf_insn), comment);
 }
 
+static int connect_prog_load_path(const char *path,
+				  enum bpf_attach_type attach_type,
+				  const char *comment)
+{
+	struct bpf_prog_load_attr attr;
+	struct bpf_object *obj;
+	int prog_fd;
+
+	memset(&attr, 0, sizeof(struct bpf_prog_load_attr));
+	attr.file = path;
+	attr.prog_type = BPF_PROG_TYPE_CGROUP_SOCK_ADDR;
+	attr.expected_attach_type = attach_type;
+
+	if (bpf_prog_load_xattr(&attr, &obj, &prog_fd)) {
+		if (comment)
+			log_err(">>> Loading %s program at %s error.\n",
+				comment, path);
+		return -1;
+	}
+
+	return prog_fd;
+}
+
+static int connect4_prog_load(enum bpf_attach_type attach_type,
+			      const char *comment)
+{
+	return connect_prog_load_path(CONNECT4_PROG_PATH, attach_type, comment);
+}
+
+static int connect6_prog_load(enum bpf_attach_type attach_type,
+			      const char *comment)
+{
+	return connect_prog_load_path(CONNECT6_PROG_PATH, attach_type, comment);
+}
+
 static void print_ip_port(int sockfd, info_fn fn, const char *fmt)
 {
 	char addr_buf[INET_NTOP_BUF];
···
 	print_ip_port(sockfd, getsockname, fmt);
 }
 
+static void print_remote_ip_port(int sockfd, const char *fmt)
+{
+	print_ip_port(sockfd, getpeername, fmt);
+}
+
 static int start_server(int type, const struct sockaddr_storage *addr,
 			socklen_t addr_len)
 {
···
 	return fd;
 }
 
+static int connect_to_server(int type, const struct sockaddr_storage *addr,
+			     socklen_t addr_len)
+{
+	int domain;
+	int fd;
+
+	domain = addr->ss_family;
+
+	if (domain != AF_INET && domain != AF_INET6) {
+		log_err("Unsupported address family");
+		return -1;
+	}
+
+	fd = socket(domain, type, 0);
+	if (fd == -1) {
+		log_err("Failed to creating client socket");
+		return -1;
+	}
+
+	if (connect(fd, (const struct sockaddr *)addr, addr_len) == -1) {
+		log_err("Fail to connect to server");
+		goto err;
+	}
+
+	print_remote_ip_port(fd, "\t   Actual: connect(%s, %d)");
+	print_local_ip_port(fd, " from (%s, %d)\n");
+
+	return 0;
+err:
+	close(fd);
+	return -1;
+}
+
 static void print_test_case_num(int domain, int type)
 {
 	static int test_num;
···
 	if (servfd == -1)
 		goto err;
 
+	printf("\tRequested: connect(%s, %d) from (*, *) ..\n", ip, port);
+	if (connect_to_server(type, &addr, addr_len))
+		goto err;
+
 	goto out;
 err:
 	err = -1;
···
 	size_t i;
 
 	for (i = 0; i < prog_cnt; ++i) {
+		printf("Load %s with invalid type (can pollute stderr) ",
+		       progs[i].name);
+		fflush(stdout);
 		progs[i].fd = progs[i].loadfn(progs[i].invalid_type, NULL);
 		if (progs[i].fd != -1) {
 			log_err("Load with invalid type accepted for %s",
 				progs[i].name);
 			goto err;
 		}
+		printf("... REJECTED\n");
+
+		printf("Load %s with valid type", progs[i].name);
 		progs[i].fd = progs[i].loadfn(progs[i].type, progs[i].name);
 		if (progs[i].fd == -1) {
 			log_err("Failed to load program %s", progs[i].name);
 			goto err;
 		}
+		printf(" ... OK\n");
+
+		printf("Attach %s with invalid type", progs[i].name);
 		if (bpf_prog_attach(progs[i].fd, cgfd, progs[i].invalid_type,
 				    BPF_F_ALLOW_OVERRIDE) != -1) {
 			log_err("Attach with invalid type accepted for %s",
 				progs[i].name);
 			goto err;
 		}
+		printf(" ... REJECTED\n");
+
+		printf("Attach %s with valid type", progs[i].name);
 		if (bpf_prog_attach(progs[i].fd, cgfd, progs[i].type,
 				    BPF_F_ALLOW_OVERRIDE) == -1) {
 			log_err("Failed to attach program %s", progs[i].name);
 			goto err;
 		}
-		printf("Attached %s program.\n", progs[i].name);
+		printf(" ... OK\n");
 	}
 
 	return 0;
···
 	struct program inet6_progs[] = {
 		{BPF_CGROUP_INET6_BIND, bind6_prog_load, -1, "bind6",
 		 BPF_CGROUP_INET4_BIND},
+		{BPF_CGROUP_INET6_CONNECT, connect6_prog_load, -1, "connect6",
+		 BPF_CGROUP_INET4_CONNECT},
 	};
 	inet6_prog_cnt = sizeof(inet6_progs) / sizeof(struct program);
 
 	struct program inet_progs[] = {
 		{BPF_CGROUP_INET4_BIND, bind4_prog_load, -1, "bind4",
 		 BPF_CGROUP_INET6_BIND},
+		{BPF_CGROUP_INET4_CONNECT, connect4_prog_load, -1, "connect4",
+		 BPF_CGROUP_INET6_CONNECT},
 	};
 	inet_prog_cnt = sizeof(inet_progs) / sizeof(struct program);
 
···
 
 int main(int argc, char **argv)
 {
+	if (argc < 2) {
+		fprintf(stderr,
+			"%s has to be run via %s.sh. Skip direct run.\n",
+			argv[0], argv[0]);
+		exit(0);
+	}
 	return run_test();
 }

tools/testing/selftests/bpf/test_sock_addr.sh

···
+#!/bin/sh
+
+set -eu
+
+ping_once()
+{
+	ping -q -c 1 -W 1 ${1%%/*} >/dev/null 2>&1
+}
+
+wait_for_ip()
+{
+	local _i
+	echo -n "Wait for testing IPv4/IPv6 to become available "
+	for _i in $(seq ${MAX_PING_TRIES}); do
+		echo -n "."
+		if ping_once ${TEST_IPv4} && ping_once ${TEST_IPv6}; then
+			echo " OK"
+			return
+		fi
+	done
+	echo 1>&2 "ERROR: Timeout waiting for test IP to become available."
+	exit 1
+}
+
+setup()
+{
+	# Create testing interfaces not to interfere with current environment.
+	ip link add dev ${TEST_IF} type veth peer name ${TEST_IF_PEER}
+	ip link set ${TEST_IF} up
+	ip link set ${TEST_IF_PEER} up
+
+	ip -4 addr add ${TEST_IPv4} dev ${TEST_IF}
+	ip -6 addr add ${TEST_IPv6} dev ${TEST_IF}
+	wait_for_ip
+}
+
+cleanup()
+{
+	ip link del ${TEST_IF} 2>/dev/null || :
+	ip link del ${TEST_IF_PEER} 2>/dev/null || :
+}
+
+main()
+{
+	trap cleanup EXIT 2 3 6 15
+	setup
+	./test_sock_addr setup_done
+}
+
+BASENAME=$(basename $0 .sh)
+TEST_IF="${BASENAME}1"
+TEST_IF_PEER="${BASENAME}2"
+TEST_IPv4="127.0.0.4/8"
+TEST_IPv6="::6/128"
+MAX_PING_TRIES=5
+
+main