selftests/bpf: Selftest for sys_bind hooks

Add selftest to work with bpf_sock_addr context from
`BPF_PROG_TYPE_CGROUP_SOCK_ADDR` programs.

Try to bind(2) on IP:port and apply:
* loads to make sure context can be read correctly, including narrow
  loads (byte, half) for IP and full-size loads (word) for all fields;
* stores to those fields allowed by verifier.

All combination from IPv4/IPv6 and TCP/UDP are tested.

Both scenarios are tested:
* valid programs can be loaded and attached;
* invalid programs can be neither loaded nor attached.

Test passes when expected data can be read from context in the
BPF-program, and after the call to bind(2) socket is bound to IP:port
pair that was written by BPF-program to the context.

Example:
  # ./test_sock_addr
  Attached bind4 program.
  Test case #1 (IPv4/TCP):
          Requested: bind(192.168.1.254, 4040) ..
             Actual: bind(127.0.0.1, 4444)
  Test case #2 (IPv4/UDP):
          Requested: bind(192.168.1.254, 4040) ..
             Actual: bind(127.0.0.1, 4444)
  Attached bind6 program.
  Test case #3 (IPv6/TCP):
          Requested: bind(face:b00c:1234:5678::abcd, 6060) ..
             Actual: bind(::1, 6666)
  Test case #4 (IPv6/UDP):
          Requested: bind(face:b00c:1234:5678::abcd, 6060) ..
             Actual: bind(::1, 6666)
  ### SUCCESS
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/include/uapi/linux/bpf.h

@@ -136,6 +136,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_CGROUP_DEVICE,
 	BPF_PROG_TYPE_SK_MSG,
 	BPF_PROG_TYPE_RAW_TRACEPOINT,
+	BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
 };
 
 enum bpf_attach_type {
@@ -147,6 +148,8 @@ enum bpf_attach_type {
 	BPF_SK_SKB_STREAM_VERDICT,
 	BPF_CGROUP_DEVICE,
 	BPF_SK_MSG_VERDICT,
+	BPF_CGROUP_INET4_BIND,
+	BPF_CGROUP_INET6_BIND,
 	__MAX_BPF_ATTACH_TYPE
 };
 
@@ -1009,6 +1012,26 @@ struct bpf_map_info {
 	__u64 netns_ino;
 } __attribute__((aligned(8)));
 
+/* User bpf_sock_addr struct to access socket fields and sockaddr struct passed
+ * by user and intended to be used by socket (e.g. to bind to, depends on
+ * attach attach type).
+ */
+struct bpf_sock_addr {
+	__u32 user_family;	/* Allows 4-byte read, but no write. */
+	__u32 user_ip4;		/* Allows 1,2,4-byte read and 4-byte write.
+				 * Stored in network byte order.
+				 */
+	__u32 user_ip6[4];	/* Allows 1,2,4-byte read an 4-byte write.
+				 * Stored in network byte order.
+				 */
+	__u32 user_port;	/* Allows 4-byte read and write.
+				 * Stored in network byte order
+				 */
+	__u32 family;		/* Allows 4-byte read, but no write */
+	__u32 type;		/* Allows 4-byte read, but no write */
+	__u32 protocol;		/* Allows 4-byte read, but no write */
+};
+
 /* User bpf_sock_ops struct to access socket values and specify request ops
  * and their replies.
  * Some of this fields are in network (bigendian) byte order and may need

tools/lib/bpf/libbpf.c

@@ -1859,6 +1859,9 @@ static void bpf_program__set_expected_attach_type(struct bpf_program *prog,
 
 #define BPF_PROG_SEC(string, ptype) BPF_PROG_SEC_FULL(string, ptype, 0)
 
+#define BPF_SA_PROG_SEC(string, ptype) \
+	BPF_PROG_SEC_FULL(string, BPF_PROG_TYPE_CGROUP_SOCK_ADDR, ptype)
+
 static const struct {
 	const char *sec;
 	size_t len;
@@ -1882,10 +1885,13 @@ static const struct {
 	BPF_PROG_SEC("sockops",		BPF_PROG_TYPE_SOCK_OPS),
 	BPF_PROG_SEC("sk_skb",		BPF_PROG_TYPE_SK_SKB),
 	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),
 };
 
 #undef BPF_PROG_SEC
 #undef BPF_PROG_SEC_FULL
+#undef BPF_SA_PROG_SEC
 
 static int bpf_program__identify_section(struct bpf_program *prog)
 {

tools/testing/selftests/bpf/Makefile

@@ -23,7 +23,7 @@ urandom_read: urandom_read.c
 
 # Order correspond to 'make run_tests' order
 TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \
-	test_align test_verifier_log test_dev_cgroup test_tcpbpf_user
+	test_align test_verifier_log test_dev_cgroup test_tcpbpf_user test_sock_addr
 
 TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test_obj_id.o \
 	test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o     \
@@ -51,6 +51,7 @@ $(TEST_GEN_PROGS): $(BPFOBJ)
 $(TEST_GEN_PROGS_EXTENDED): $(OUTPUT)/libbpf.a
 
 $(OUTPUT)/test_dev_cgroup: cgroup_helpers.c
+$(OUTPUT)/test_sock_addr: cgroup_helpers.c
 
 .PHONY: force
 

tools/testing/selftests/bpf/test_sock_addr.c

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <arpa/inet.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#include <linux/filter.h>
+
+#include <bpf/bpf.h>
+
+#include "cgroup_helpers.h"
+
+#define CG_PATH	"/foo"
+
+#define SERV4_IP		"192.168.1.254"
+#define SERV4_REWRITE_IP	"127.0.0.1"
+#define SERV4_PORT		4040
+#define SERV4_REWRITE_PORT	4444
+
+#define SERV6_IP		"face:b00c:1234:5678::abcd"
+#define SERV6_REWRITE_IP	"::1"
+#define SERV6_PORT		6060
+#define SERV6_REWRITE_PORT	6666
+
+#define INET_NTOP_BUF	40
+
+typedef int (*load_fn)(enum bpf_attach_type, const char *comment);
+typedef int (*info_fn)(int, struct sockaddr *, socklen_t *);
+
+struct program {
+	enum bpf_attach_type type;
+	load_fn	loadfn;
+	int fd;
+	const char *name;
+	enum bpf_attach_type invalid_type;
+};
+
+char bpf_log_buf[BPF_LOG_BUF_SIZE];
+
+static int mk_sockaddr(int domain, const char *ip, unsigned short port,
+		       struct sockaddr *addr, socklen_t addr_len)
+{
+	struct sockaddr_in6 *addr6;
+	struct sockaddr_in *addr4;
+
+	if (domain != AF_INET && domain != AF_INET6) {
+		log_err("Unsupported address family");
+		return -1;
+	}
+
+	memset(addr, 0, addr_len);
+
+	if (domain == AF_INET) {
+		if (addr_len < sizeof(struct sockaddr_in))
+			return -1;
+		addr4 = (struct sockaddr_in *)addr;
+		addr4->sin_family = domain;
+		addr4->sin_port = htons(port);
+		if (inet_pton(domain, ip, (void *)&addr4->sin_addr) != 1) {
+			log_err("Invalid IPv4: %s", ip);
+			return -1;
+		}
+	} else if (domain == AF_INET6) {
+		if (addr_len < sizeof(struct sockaddr_in6))
+			return -1;
+		addr6 = (struct sockaddr_in6 *)addr;
+		addr6->sin6_family = domain;
+		addr6->sin6_port = htons(port);
+		if (inet_pton(domain, ip, (void *)&addr6->sin6_addr) != 1) {
+			log_err("Invalid IPv6: %s", ip);
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+static int load_insns(enum bpf_attach_type attach_type,
+		      const struct bpf_insn *insns, size_t insns_cnt,
+		      const char *comment)
+{
+	struct bpf_load_program_attr load_attr;
+	int ret;
+
+	memset(&load_attr, 0, sizeof(struct bpf_load_program_attr));
+	load_attr.prog_type = BPF_PROG_TYPE_CGROUP_SOCK_ADDR;
+	load_attr.expected_attach_type = attach_type;
+	load_attr.insns = insns;
+	load_attr.insns_cnt = insns_cnt;
+	load_attr.license = "GPL";
+
+	ret = bpf_load_program_xattr(&load_attr, bpf_log_buf, BPF_LOG_BUF_SIZE);
+	if (ret < 0 && comment) {
+		log_err(">>> Loading %s program error.\n"
+			">>> Output from verifier:\n%s\n-------\n",
+			comment, bpf_log_buf);
+	}
+
+	return ret;
+}
+
+/* [1] These testing programs try to read different context fields, including
+ * narrow loads of different sizes from user_ip4 and user_ip6, and write to
+ * those allowed to be overridden.
+ *
+ * [2] BPF_LD_IMM64 & BPF_JMP_REG are used below whenever there is a need to
+ * compare a register with unsigned 32bit integer. BPF_JMP_IMM can't be used
+ * in such cases since it accepts only _signed_ 32bit integer as IMM
+ * argument. Also note that BPF_LD_IMM64 contains 2 instructions what matters
+ * to count jumps properly.
+ */
+
+static int bind4_prog_load(enum bpf_attach_type attach_type,
+			   const char *comment)
+{
+	union {
+		uint8_t u4_addr8[4];
+		uint16_t u4_addr16[2];
+		uint32_t u4_addr32;
+	} ip4;
+	struct sockaddr_in addr4_rw;
+
+	if (inet_pton(AF_INET, SERV4_IP, (void *)&ip4) != 1) {
+		log_err("Invalid IPv4: %s", SERV4_IP);
+		return -1;
+	}
+
+	if (mk_sockaddr(AF_INET, SERV4_REWRITE_IP, SERV4_REWRITE_PORT,
+			(struct sockaddr *)&addr4_rw, sizeof(addr4_rw)) == -1)
+		return -1;
+
+	/* See [1]. */
+	struct bpf_insn insns[] = {
+		BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
+
+		/* if (sk.family == AF_INET && */
+		BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, family)),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_7, AF_INET, 16),
+
+		/*     (sk.type == SOCK_DGRAM || sk.type == SOCK_STREAM) && */
+		BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, type)),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_7, SOCK_DGRAM, 1),
+		BPF_JMP_A(1),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_7, SOCK_STREAM, 12),
+
+		/*     1st_byte_of_user_ip4 == expected && */
+		BPF_LDX_MEM(BPF_B, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, user_ip4)),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip4.u4_addr8[0], 10),
+
+		/*     1st_half_of_user_ip4 == expected && */
+		BPF_LDX_MEM(BPF_H, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, user_ip4)),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip4.u4_addr16[0], 8),
+
+		/*     whole_user_ip4 == expected) { */
+		BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, user_ip4)),
+		BPF_LD_IMM64(BPF_REG_8, ip4.u4_addr32), /* See [2]. */
+		BPF_JMP_REG(BPF_JNE, BPF_REG_7, BPF_REG_8, 4),
+
+		/*      user_ip4 = addr4_rw.sin_addr */
+		BPF_MOV32_IMM(BPF_REG_7, addr4_rw.sin_addr.s_addr),
+		BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_7,
+			    offsetof(struct bpf_sock_addr, user_ip4)),
+
+		/*      user_port = addr4_rw.sin_port */
+		BPF_MOV32_IMM(BPF_REG_7, addr4_rw.sin_port),
+		BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_7,
+			    offsetof(struct bpf_sock_addr, user_port)),
+		/* } */
+
+		/* return 1 */
+		BPF_MOV64_IMM(BPF_REG_0, 1),
+		BPF_EXIT_INSN(),
+	};
+
+	return load_insns(attach_type, insns,
+			  sizeof(insns) / sizeof(struct bpf_insn), comment);
+}
+
+static int bind6_prog_load(enum bpf_attach_type attach_type,
+			   const char *comment)
+{
+	struct sockaddr_in6 addr6_rw;
+	struct in6_addr ip6;
+
+	if (inet_pton(AF_INET6, SERV6_IP, (void *)&ip6) != 1) {
+		log_err("Invalid IPv6: %s", SERV6_IP);
+		return -1;
+	}
+
+	if (mk_sockaddr(AF_INET6, SERV6_REWRITE_IP, SERV6_REWRITE_PORT,
+			(struct sockaddr *)&addr6_rw, sizeof(addr6_rw)) == -1)
+		return -1;
+
+	/* See [1]. */
+	struct bpf_insn insns[] = {
+		BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
+
+		/* if (sk.family == AF_INET6 && */
+		BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, family)),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_7, AF_INET6, 18),
+
+		/*            5th_byte_of_user_ip6 == expected && */
+		BPF_LDX_MEM(BPF_B, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, user_ip6[1])),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip6.s6_addr[4], 16),
+
+		/*            3rd_half_of_user_ip6 == expected && */
+		BPF_LDX_MEM(BPF_H, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, user_ip6[1])),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip6.s6_addr16[2], 14),
+
+		/*            last_word_of_user_ip6 == expected) { */
+		BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, user_ip6[3])),
+		BPF_LD_IMM64(BPF_REG_8, ip6.s6_addr32[3]),  /* See [2]. */
+		BPF_JMP_REG(BPF_JNE, BPF_REG_7, BPF_REG_8, 10),
+
+
+#define STORE_IPV6_WORD(N)						       \
+		BPF_MOV32_IMM(BPF_REG_7, addr6_rw.sin6_addr.s6_addr32[N]),     \
+		BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_7,		       \
+			    offsetof(struct bpf_sock_addr, user_ip6[N]))
+
+		/*      user_ip6 = addr6_rw.sin6_addr */
+		STORE_IPV6_WORD(0),
+		STORE_IPV6_WORD(1),
+		STORE_IPV6_WORD(2),
+		STORE_IPV6_WORD(3),
+
+		/*      user_port = addr6_rw.sin6_port */
+		BPF_MOV32_IMM(BPF_REG_7, addr6_rw.sin6_port),
+		BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_7,
+			    offsetof(struct bpf_sock_addr, user_port)),
+
+		/* } */
+
+		/* return 1 */
+		BPF_MOV64_IMM(BPF_REG_0, 1),
+		BPF_EXIT_INSN(),
+	};
+
+	return load_insns(attach_type, insns,
+			  sizeof(insns) / sizeof(struct bpf_insn), comment);
+}
+
+static void print_ip_port(int sockfd, info_fn fn, const char *fmt)
+{
+	char addr_buf[INET_NTOP_BUF];
+	struct sockaddr_storage addr;
+	struct sockaddr_in6 *addr6;
+	struct sockaddr_in *addr4;
+	socklen_t addr_len;
+	unsigned short port;
+	void *nip;
+
+	addr_len = sizeof(struct sockaddr_storage);
+	memset(&addr, 0, addr_len);
+
+	if (fn(sockfd, (struct sockaddr *)&addr, (socklen_t *)&addr_len) == 0) {
+		if (addr.ss_family == AF_INET) {
+			addr4 = (struct sockaddr_in *)&addr;
+			nip = (void *)&addr4->sin_addr;
+			port = ntohs(addr4->sin_port);
+		} else if (addr.ss_family == AF_INET6) {
+			addr6 = (struct sockaddr_in6 *)&addr;
+			nip = (void *)&addr6->sin6_addr;
+			port = ntohs(addr6->sin6_port);
+		} else {
+			return;
+		}
+		const char *addr_str =
+			inet_ntop(addr.ss_family, nip, addr_buf, INET_NTOP_BUF);
+		printf(fmt, addr_str ? addr_str : "??", port);
+	}
+}
+
+static void print_local_ip_port(int sockfd, const char *fmt)
+{
+	print_ip_port(sockfd, getsockname, fmt);
+}
+
+static int start_server(int type, const struct sockaddr_storage *addr,
+			socklen_t addr_len)
+{
+
+	int fd;
+
+	fd = socket(addr->ss_family, type, 0);
+	if (fd == -1) {
+		log_err("Failed to create server socket");
+		goto out;
+	}
+
+	if (bind(fd, (const struct sockaddr *)addr, addr_len) == -1) {
+		log_err("Failed to bind server socket");
+		goto close_out;
+	}
+
+	if (type == SOCK_STREAM) {
+		if (listen(fd, 128) == -1) {
+			log_err("Failed to listen on server socket");
+			goto close_out;
+		}
+	}
+
+	print_local_ip_port(fd, "\t   Actual: bind(%s, %d)\n");
+
+	goto out;
+close_out:
+	close(fd);
+	fd = -1;
+out:
+	return fd;
+}
+
+static void print_test_case_num(int domain, int type)
+{
+	static int test_num;
+
+	printf("Test case #%d (%s/%s):\n", ++test_num,
+	       (domain == AF_INET ? "IPv4" :
+		domain == AF_INET6 ? "IPv6" :
+		"unknown_domain"),
+	       (type == SOCK_STREAM ? "TCP" :
+		type == SOCK_DGRAM ? "UDP" :
+		"unknown_type"));
+}
+
+static int run_test_case(int domain, int type, const char *ip,
+			 unsigned short port)
+{
+	struct sockaddr_storage addr;
+	socklen_t addr_len = sizeof(addr);
+	int servfd = -1;
+	int err = 0;
+
+	print_test_case_num(domain, type);
+
+	if (mk_sockaddr(domain, ip, port, (struct sockaddr *)&addr,
+			addr_len) == -1)
+		return -1;
+
+	printf("\tRequested: bind(%s, %d) ..\n", ip, port);
+	servfd = start_server(type, &addr, addr_len);
+	if (servfd == -1)
+		goto err;
+
+	goto out;
+err:
+	err = -1;
+out:
+	close(servfd);
+	return err;
+}
+
+static void close_progs_fds(struct program *progs, size_t prog_cnt)
+{
+	size_t i;
+
+	for (i = 0; i < prog_cnt; ++i) {
+		close(progs[i].fd);
+		progs[i].fd = -1;
+	}
+}
+
+static int load_and_attach_progs(int cgfd, struct program *progs,
+				 size_t prog_cnt)
+{
+	size_t i;
+
+	for (i = 0; i < prog_cnt; ++i) {
+		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;
+		}
+		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;
+		}
+		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;
+		}
+		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);
+	}
+
+	return 0;
+err:
+	close_progs_fds(progs, prog_cnt);
+	return -1;
+}
+
+static int run_domain_test(int domain, int cgfd, struct program *progs,
+			   size_t prog_cnt, const char *ip, unsigned short port)
+{
+	int err = 0;
+
+	if (load_and_attach_progs(cgfd, progs, prog_cnt) == -1)
+		goto err;
+
+	if (run_test_case(domain, SOCK_STREAM, ip, port) == -1)
+		goto err;
+
+	if (run_test_case(domain, SOCK_DGRAM, ip, port) == -1)
+		goto err;
+
+	goto out;
+err:
+	err = -1;
+out:
+	close_progs_fds(progs, prog_cnt);
+	return err;
+}
+
+static int run_test(void)
+{
+	size_t inet6_prog_cnt;
+	size_t inet_prog_cnt;
+	int cgfd = -1;
+	int err = 0;
+
+	struct program inet6_progs[] = {
+		{BPF_CGROUP_INET6_BIND, bind6_prog_load, -1, "bind6",
+		 BPF_CGROUP_INET4_BIND},
+	};
+	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},
+	};
+	inet_prog_cnt = sizeof(inet_progs) / sizeof(struct program);
+
+	if (setup_cgroup_environment())
+		goto err;
+
+	cgfd = create_and_get_cgroup(CG_PATH);
+	if (!cgfd)
+		goto err;
+
+	if (join_cgroup(CG_PATH))
+		goto err;
+
+	if (run_domain_test(AF_INET, cgfd, inet_progs, inet_prog_cnt, SERV4_IP,
+			    SERV4_PORT) == -1)
+		goto err;
+
+	if (run_domain_test(AF_INET6, cgfd, inet6_progs, inet6_prog_cnt,
+			    SERV6_IP, SERV6_PORT) == -1)
+		goto err;
+
+	goto out;
+err:
+	err = -1;
+out:
+	close(cgfd);
+	cleanup_cgroup_environment();
+	printf(err ? "### FAIL\n" : "### SUCCESS\n");
+	return err;
+}
+
+int main(int argc, char **argv)
+{
+	return run_test();
+}