samples/bpf: Update cgroup socket examples to use uid gid helper

Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

samples/bpf/sock_flags_kern.c

@@ -9,8 +9,13 @@ SEC("cgroup/sock1")
 int bpf_prog1(struct bpf_sock *sk)
 {
 	char fmt[] = "socket: family %d type %d protocol %d\n";
+	char fmt2[] = "socket: uid %u gid %u\n";
+	__u64 gid_uid = bpf_get_current_uid_gid();
+	__u32 uid = gid_uid & 0xffffffff;
+	__u32 gid = gid_uid >> 32;
 
 	bpf_trace_printk(fmt, sizeof(fmt), sk->family, sk->type, sk->protocol);
+	bpf_trace_printk(fmt2, sizeof(fmt2), uid, gid);
 
 	/* block PF_INET6, SOCK_RAW, IPPROTO_ICMPV6 sockets
 	 * ie., make ping6 fail

samples/bpf/test_cgrp2_sock.c

@@ -46,8 +46,18 @@ static int prog_load(__u32 idx, __u32 mark, __u32 prio)
 
 	/* set mark on socket */
 	struct bpf_insn prog_mark[] = {
-		BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+		/* get uid of process */
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+			     BPF_FUNC_get_current_uid_gid),
+		BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xffffffff),
+
+		/* if uid is 0, use given mark, else use the uid as the mark */
+		BPF_MOV64_REG(BPF_REG_3, BPF_REG_0),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
 		BPF_MOV64_IMM(BPF_REG_3, mark),
+
+		/* set the mark on the new socket */
+		BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
 		BPF_MOV64_IMM(BPF_REG_2, offsetof(struct bpf_sock, mark)),
 		BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_3, offsetof(struct bpf_sock, mark)),
 	};