bpf: Add getter and setter for SO_REUSEPORT through bpf_{g,s}etsockopt

Augment the current set of options that are accessible via
bpf_{g,s}etsockopt to also support SO_REUSEPORT.
Signed-off-by: Manu Bretelle <chantra@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210310182305.1910312-1-chantra@fb.com

net/core/filter.c

@@ -4729,6 +4729,9 @@ static int _bpf_setsockopt(struct sock *sk, int level, int optname,
 				sk->sk_prot->keepalive(sk, valbool);
 			sock_valbool_flag(sk, SOCK_KEEPOPEN, valbool);
 			break;
+		case SO_REUSEPORT:
+			sk->sk_reuseport = valbool;
+			break;
 		default:
 			ret = -EINVAL;
 		}
@@ -4898,6 +4901,9 @@ static int _bpf_getsockopt(struct sock *sk, int level, int optname,
 		case SO_BINDTOIFINDEX:
 			*((int *)optval) = sk->sk_bound_dev_if;
 			break;
+		case SO_REUSEPORT:
+			*((int *)optval) = sk->sk_reuseport;
+			break;
 		default:
 			goto err_clear;
 		}

tools/testing/selftests/bpf/progs/bind4_prog.c

@@ -57,6 +57,27 @@ static __inline int bind_to_device(struct bpf_sock_addr *ctx)
 	return 0;
 }
 
+static __inline int bind_reuseport(struct bpf_sock_addr *ctx)
+{
+	int val = 1;
+
+	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
+			   &val, sizeof(val)))
+		return 1;
+	if (bpf_getsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
+			   &val, sizeof(val)) || !val)
+		return 1;
+	val = 0;
+	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
+			   &val, sizeof(val)))
+		return 1;
+	if (bpf_getsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
+			   &val, sizeof(val)) || val)
+		return 1;
+
+	return 0;
+}
+
 static __inline int misc_opts(struct bpf_sock_addr *ctx, int opt)
 {
 	int old, tmp, new = 0xeb9f;
@@ -127,6 +148,10 @@ int bind_v4_prog(struct bpf_sock_addr *ctx)
 	if (misc_opts(ctx, SO_MARK) || misc_opts(ctx, SO_PRIORITY))
 		return 0;
 
+	/* Set reuseport and unset */
+	if (bind_reuseport(ctx))
+		return 0;
+
 	ctx->user_ip4 = bpf_htonl(SERV4_REWRITE_IP);
 	ctx->user_port = bpf_htons(SERV4_REWRITE_PORT);
 

tools/testing/selftests/bpf/progs/bind6_prog.c

@@ -63,6 +63,27 @@ static __inline int bind_to_device(struct bpf_sock_addr *ctx)
 	return 0;
 }
 
+static __inline int bind_reuseport(struct bpf_sock_addr *ctx)
+{
+	int val = 1;
+
+	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
+			   &val, sizeof(val)))
+		return 1;
+	if (bpf_getsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
+			   &val, sizeof(val)) || !val)
+		return 1;
+	val = 0;
+	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
+			   &val, sizeof(val)))
+		return 1;
+	if (bpf_getsockopt(ctx, SOL_SOCKET, SO_REUSEPORT,
+			   &val, sizeof(val)) || val)
+		return 1;
+
+	return 0;
+}
+
 static __inline int misc_opts(struct bpf_sock_addr *ctx, int opt)
 {
 	int old, tmp, new = 0xeb9f;
@@ -141,6 +162,10 @@ int bind_v6_prog(struct bpf_sock_addr *ctx)
 	if (misc_opts(ctx, SO_MARK) || misc_opts(ctx, SO_PRIORITY))
 		return 0;
 
+	/* Set reuseport and unset */
+	if (bind_reuseport(ctx))
+		return 0;
+
 	ctx->user_ip6[0] = bpf_htonl(SERV6_REWRITE_IP_0);
 	ctx->user_ip6[1] = bpf_htonl(SERV6_REWRITE_IP_1);
 	ctx->user_ip6[2] = bpf_htonl(SERV6_REWRITE_IP_2);