bpf: Add SO_KEEPALIVE and related options to bpf_setsockopt

This patch adds support of SO_KEEPALIVE flag and TCP related options
to bpf_setsockopt() routine. This is helpful if we want to enable or tune
TCP keepalive for applications which don't do it in the userspace code.

v3:
  - update kernel-doc in uapi (Nikita Vetoshkin <nekto0n@yandex-team.ru>)

v4:
  - update kernel-doc in tools too (Alexei Starovoitov)
  - add test to selftests (Alexei Starovoitov)

Signed-off-by: Dmitry Yakunin <zeil@yandex-team.ru>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200620153052.9439-3-zeil@yandex-team.ru

include/uapi/linux/bpf.h

@@ -1621,10 +1621,13 @@ union bpf_attr {
  *
  * 		* **SOL_SOCKET**, which supports the following *optname*\ s:
  * 		  **SO_RCVBUF**, **SO_SNDBUF**, **SO_MAX_PACING_RATE**,
- * 		  **SO_PRIORITY**, **SO_RCVLOWAT**, **SO_MARK**.
+ * 		  **SO_PRIORITY**, **SO_RCVLOWAT**, **SO_MARK**,
+ * 		  **SO_BINDTODEVICE**, **SO_KEEPALIVE**.
  * 		* **IPPROTO_TCP**, which supports the following *optname*\ s:
  * 		  **TCP_CONGESTION**, **TCP_BPF_IW**,
- * 		  **TCP_BPF_SNDCWND_CLAMP**.
+ * 		  **TCP_BPF_SNDCWND_CLAMP**, **TCP_SAVE_SYN**,
+ * 		  **TCP_KEEPIDLE**, **TCP_KEEPINTVL**, **TCP_KEEPCNT**,
+ * 		  **TCP_SYNCNT**, **TCP_USER_TIMEOUT**.
  * 		* **IPPROTO_IP**, which supports *optname* **IP_TOS**.
  * 		* **IPPROTO_IPV6**, which supports *optname* **IPV6_TCLASS**.
  * 	Return

net/core/filter.c

@@ -4289,10 +4289,10 @@ static int _bpf_setsockopt(struct sock *sk, int level, int optname,
 			   char *optval, int optlen, u32 flags)
 {
 	char devname[IFNAMSIZ];
+	int val, valbool;
 	struct net *net;
 	int ifindex;
 	int ret = 0;
-	int val;
 
 	if (!sk_fullsock(sk))
 		return -EINVAL;
@@ -4303,6 +4303,7 @@ static int _bpf_setsockopt(struct sock *sk, int level, int optname,
 		if (optlen != sizeof(int) && optname != SO_BINDTODEVICE)
 			return -EINVAL;
 		val = *((int *)optval);
+		valbool = val ? 1 : 0;
 
 		/* Only some socketops are supported */
 		switch (optname) {
@@ -4361,6 +4362,11 @@ static int _bpf_setsockopt(struct sock *sk, int level, int optname,
 			}
 			ret = sock_bindtoindex(sk, ifindex, false);
 			break;
+		case SO_KEEPALIVE:
+			if (sk->sk_prot->keepalive)
+				sk->sk_prot->keepalive(sk, valbool);
+			sock_valbool_flag(sk, SOCK_KEEPOPEN, valbool);
+			break;
 		default:
 			ret = -EINVAL;
 		}
@@ -4421,6 +4427,7 @@ static int _bpf_setsockopt(struct sock *sk, int level, int optname,
 			ret = tcp_set_congestion_control(sk, name, false,
 							 reinit, true);
 		} else {
+			struct inet_connection_sock *icsk = inet_csk(sk);
 			struct tcp_sock *tp = tcp_sk(sk);
 
 			if (optlen != sizeof(int))
@@ -4449,6 +4456,33 @@ static int _bpf_setsockopt(struct sock *sk, int level, int optname,
 				else
 					tp->save_syn = val;
 				break;
+			case TCP_KEEPIDLE:
+				ret = tcp_sock_set_keepidle_locked(sk, val);
+				break;
+			case TCP_KEEPINTVL:
+				if (val < 1 || val > MAX_TCP_KEEPINTVL)
+					ret = -EINVAL;
+				else
+					tp->keepalive_intvl = val * HZ;
+				break;
+			case TCP_KEEPCNT:
+				if (val < 1 || val > MAX_TCP_KEEPCNT)
+					ret = -EINVAL;
+				else
+					tp->keepalive_probes = val;
+				break;
+			case TCP_SYNCNT:
+				if (val < 1 || val > MAX_TCP_SYNCNT)
+					ret = -EINVAL;
+				else
+					icsk->icsk_syn_retries = val;
+				break;
+			case TCP_USER_TIMEOUT:
+				if (val < 0)
+					ret = -EINVAL;
+				else
+					icsk->icsk_user_timeout = val;
+				break;
 			default:
 				ret = -EINVAL;
 			}

tools/include/uapi/linux/bpf.h

@@ -1621,10 +1621,13 @@ union bpf_attr {
  *
  * 		* **SOL_SOCKET**, which supports the following *optname*\ s:
  * 		  **SO_RCVBUF**, **SO_SNDBUF**, **SO_MAX_PACING_RATE**,
- * 		  **SO_PRIORITY**, **SO_RCVLOWAT**, **SO_MARK**.
+ * 		  **SO_PRIORITY**, **SO_RCVLOWAT**, **SO_MARK**,
+ * 		  **SO_BINDTODEVICE**, **SO_KEEPALIVE**.
  * 		* **IPPROTO_TCP**, which supports the following *optname*\ s:
  * 		  **TCP_CONGESTION**, **TCP_BPF_IW**,
- * 		  **TCP_BPF_SNDCWND_CLAMP**.
+ * 		  **TCP_BPF_SNDCWND_CLAMP**, **TCP_SAVE_SYN**,
+ * 		  **TCP_KEEPIDLE**, **TCP_KEEPINTVL**, **TCP_KEEPCNT**,
+ * 		  **TCP_SYNCNT**, **TCP_USER_TIMEOUT**.
  * 		* **IPPROTO_IP**, which supports *optname* **IP_TOS**.
  * 		* **IPPROTO_IPV6**, which supports *optname* **IPV6_TCLASS**.
  * 	Return

tools/testing/selftests/bpf/progs/connect4_prog.c

@@ -104,6 +104,30 @@ static __inline int bind_to_device(struct bpf_sock_addr *ctx)
 	return 0;
 }
 
+static __inline int set_keepalive(struct bpf_sock_addr *ctx)
+{
+	int zero = 0, one = 1;
+
+	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof(one)))
+		return 1;
+	if (ctx->type == SOCK_STREAM) {
+		if (bpf_setsockopt(ctx, SOL_TCP, TCP_KEEPIDLE, &one, sizeof(one)))
+			return 1;
+		if (bpf_setsockopt(ctx, SOL_TCP, TCP_KEEPINTVL, &one, sizeof(one)))
+			return 1;
+		if (bpf_setsockopt(ctx, SOL_TCP, TCP_KEEPCNT, &one, sizeof(one)))
+			return 1;
+		if (bpf_setsockopt(ctx, SOL_TCP, TCP_SYNCNT, &one, sizeof(one)))
+			return 1;
+		if (bpf_setsockopt(ctx, SOL_TCP, TCP_USER_TIMEOUT, &one, sizeof(one)))
+			return 1;
+	}
+	if (bpf_setsockopt(ctx, SOL_SOCKET, SO_KEEPALIVE, &zero, sizeof(zero)))
+		return 1;
+
+	return 0;
+}
+
 SEC("cgroup/connect4")
 int connect_v4_prog(struct bpf_sock_addr *ctx)
 {
@@ -121,6 +145,9 @@ int connect_v4_prog(struct bpf_sock_addr *ctx)
 	if (bind_to_device(ctx))
 		return 0;
 
+	if (set_keepalive(ctx))
+		return 0;
+
 	if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM)
 		return 0;
 	else if (ctx->type == SOCK_STREAM)