samples: bpf: add skb->field examples and tests

- modify sockex1 example to count number of bytes in outgoing packets
- modify sockex2 example to count number of bytes and packets per flow
- add 4 stress tests that exercise 'skb->field' code path of verifier

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

samples/bpf/sockex1_kern.c

@@ -1,5 +1,6 @@
 #include <uapi/linux/bpf.h>
 #include <uapi/linux/if_ether.h>
+#include <uapi/linux/if_packet.h>
 #include <uapi/linux/ip.h>
 #include "bpf_helpers.h"
 
@@ -11,14 +12,17 @@ struct bpf_map_def SEC("maps") my_map = {
 };
 
 SEC("socket1")
-int bpf_prog1(struct sk_buff *skb)
+int bpf_prog1(struct __sk_buff *skb)
 {
 	int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
 	long *value;
 
+	if (skb->pkt_type != PACKET_OUTGOING)
+		return 0;
+
 	value = bpf_map_lookup_elem(&my_map, &index);
 	if (value)
-		__sync_fetch_and_add(value, 1);
+		__sync_fetch_and_add(value, skb->len);
 
 	return 0;
 }

samples/bpf/sockex1_user.c

@@ -40,7 +40,7 @@ int main(int ac, char **argv)
 		key = IPPROTO_ICMP;
 		assert(bpf_lookup_elem(map_fd[0], &key, &icmp_cnt) == 0);
 
-		printf("TCP %lld UDP %lld ICMP %lld packets\n",
+		printf("TCP %lld UDP %lld ICMP %lld bytes\n",
 		       tcp_cnt, udp_cnt, icmp_cnt);
 		sleep(1);
 	}

samples/bpf/sockex2_kern.c

@@ -42,13 +42,13 @@ static inline int proto_ports_offset(__u64 proto)
 	}
 }
 
-static inline int ip_is_fragment(struct sk_buff *ctx, __u64 nhoff)
+static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff)
 {
 	return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off))
 		& (IP_MF | IP_OFFSET);
 }
 
-static inline __u32 ipv6_addr_hash(struct sk_buff *ctx, __u64 off)
+static inline __u32 ipv6_addr_hash(struct __sk_buff *ctx, __u64 off)
 {
 	__u64 w0 = load_word(ctx, off);
 	__u64 w1 = load_word(ctx, off + 4);
@@ -58,7 +58,7 @@ static inline __u32 ipv6_addr_hash(struct sk_buff *ctx, __u64 off)
 	return (__u32)(w0 ^ w1 ^ w2 ^ w3);
 }
 
-static inline __u64 parse_ip(struct sk_buff *skb, __u64 nhoff, __u64 *ip_proto,
+static inline __u64 parse_ip(struct __sk_buff *skb, __u64 nhoff, __u64 *ip_proto,
 			     struct flow_keys *flow)
 {
 	__u64 verlen;
@@ -82,7 +82,7 @@ static inline __u64 parse_ip(struct sk_buff *skb, __u64 nhoff, __u64 *ip_proto,
 	return nhoff;
 }
 
-static inline __u64 parse_ipv6(struct sk_buff *skb, __u64 nhoff, __u64 *ip_proto,
+static inline __u64 parse_ipv6(struct __sk_buff *skb, __u64 nhoff, __u64 *ip_proto,
 			       struct flow_keys *flow)
 {
 	*ip_proto = load_byte(skb,
@@ -96,7 +96,7 @@ static inline __u64 parse_ipv6(struct sk_buff *skb, __u64 nhoff, __u64 *ip_proto
 	return nhoff;
 }
 
-static inline bool flow_dissector(struct sk_buff *skb, struct flow_keys *flow)
+static inline bool flow_dissector(struct __sk_buff *skb, struct flow_keys *flow)
 {
 	__u64 nhoff = ETH_HLEN;
 	__u64 ip_proto;
@@ -183,18 +183,23 @@ static inline bool flow_dissector(struct sk_buff *skb, struct flow_keys *flow)
 	return true;
 }
 
+struct pair {
+	long packets;
+	long bytes;
+};
+
 struct bpf_map_def SEC("maps") hash_map = {
 	.type = BPF_MAP_TYPE_HASH,
 	.key_size = sizeof(__be32),
-	.value_size = sizeof(long),
+	.value_size = sizeof(struct pair),
 	.max_entries = 1024,
 };
 
 SEC("socket2")
-int bpf_prog2(struct sk_buff *skb)
+int bpf_prog2(struct __sk_buff *skb)
 {
 	struct flow_keys flow;
-	long *value;
+	struct pair *value;
 	u32 key;
 
 	if (!flow_dissector(skb, &flow))
@@ -203,9 +208,10 @@ int bpf_prog2(struct sk_buff *skb)
 	key = flow.dst;
 	value = bpf_map_lookup_elem(&hash_map, &key);
 	if (value) {
-		__sync_fetch_and_add(value, 1);
+		__sync_fetch_and_add(&value->packets, 1);
+		__sync_fetch_and_add(&value->bytes, skb->len);
 	} else {
-		long val = 1;
+		struct pair val = {1, skb->len};
 
 		bpf_map_update_elem(&hash_map, &key, &val, BPF_ANY);
 	}

samples/bpf/sockex2_user.c

@@ -6,6 +6,11 @@
 #include <unistd.h>
 #include <arpa/inet.h>
 
+struct pair {
+	__u64 packets;
+	__u64 bytes;
+};
+
 int main(int ac, char **argv)
 {
 	char filename[256];
@@ -29,13 +34,13 @@ int main(int ac, char **argv)
 
 	for (i = 0; i < 5; i++) {
 		int key = 0, next_key;
-		long long value;
+		struct pair value;
 
 		while (bpf_get_next_key(map_fd[0], &key, &next_key) == 0) {
 			bpf_lookup_elem(map_fd[0], &next_key, &value);
-			printf("ip %s count %lld\n",
+			printf("ip %s bytes %lld packets %lld\n",
 			       inet_ntoa((struct in_addr){htonl(next_key)}),
-			       value);
+			       value.bytes, value.packets);
 			key = next_key;
 		}
 		sleep(1);

samples/bpf/test_verifier.c

@@ -14,6 +14,7 @@
 #include <linux/unistd.h>
 #include <string.h>
 #include <linux/filter.h>
+#include <stddef.h>
 #include "libbpf.h"
 
 #define MAX_INSNS 512
@@ -642,6 +643,75 @@ static struct bpf_test tests[] = {
 		},
 		.result = ACCEPT,
 	},
+	{
+		"access skb fields ok",
+		.insns = {
+			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+				    offsetof(struct __sk_buff, len)),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 1),
+			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+				    offsetof(struct __sk_buff, mark)),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 1),
+			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+				    offsetof(struct __sk_buff, pkt_type)),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 1),
+			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+				    offsetof(struct __sk_buff, queue_mapping)),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),
+			BPF_EXIT_INSN(),
+		},
+		.result = ACCEPT,
+	},
+	{
+		"access skb fields bad1",
+		.insns = {
+			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1, -4),
+			BPF_EXIT_INSN(),
+		},
+		.errstr = "invalid bpf_context access",
+		.result = REJECT,
+	},
+	{
+		"access skb fields bad2",
+		.insns = {
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_1, 0, 9),
+			BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+			BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+			BPF_LD_MAP_FD(BPF_REG_1, 0),
+			BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
+			BPF_EXIT_INSN(),
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+				    offsetof(struct __sk_buff, pkt_type)),
+			BPF_EXIT_INSN(),
+		},
+		.fixup = {4},
+		.errstr = "different pointers",
+		.result = REJECT,
+	},
+	{
+		"access skb fields bad3",
+		.insns = {
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_1, 0, 2),
+			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+				    offsetof(struct __sk_buff, pkt_type)),
+			BPF_EXIT_INSN(),
+			BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+			BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+			BPF_LD_MAP_FD(BPF_REG_1, 0),
+			BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
+			BPF_EXIT_INSN(),
+			BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+			BPF_JMP_IMM(BPF_JA, 0, 0, -12),
+		},
+		.fixup = {6},
+		.errstr = "different pointers",
+		.result = REJECT,
+	},
 };
 
 static int probe_filter_length(struct bpf_insn *fp)