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Commit d1361840 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: fix SO_RCVLOWAT and RCVBUF autotuning 



Applications might use SO_RCVLOWAT on TCP socket hoping to receive
one [E]POLLIN event only when a given amount of bytes are ready in socket
receive queue.

Problem is that receive autotuning is not aware of this constraint,
meaning sk_rcvbuf might be too small to allow all bytes to be stored.

Add a new (struct proto_ops)->set_rcvlowat method so that a protocol
can override the default setsockopt(SO_RCVLOWAT) behavior.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 10b19aea

include/linux/net.h

+1 −0
Original line number Diff line number Diff line
@@ -197,6 +197,7 @@ struct proto_ops { 
					   int offset, size_t size, int flags);

	int		(*sendmsg_locked)(struct sock *sk, struct msghdr *msg,

					  size_t size);

	int		(*set_rcvlowat)(struct sock *sk, int val);

};



#define DECLARE_SOCKADDR(type, dst, src)	\

include/net/tcp.h

+1 −0
Original line number Diff line number Diff line
@@ -402,6 +402,7 @@ void tcp_set_keepalive(struct sock *sk, int val); 
void tcp_syn_ack_timeout(const struct request_sock *req);

int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,

		int flags, int *addr_len);

int tcp_set_rcvlowat(struct sock *sk, int val);

void tcp_parse_options(const struct net *net, const struct sk_buff *skb,

		       struct tcp_options_received *opt_rx,

		       int estab, struct tcp_fastopen_cookie *foc);

net/core/sock.c

+4 −1
Original line number Diff line number Diff line
@@ -905,6 +905,9 @@ int sock_setsockopt(struct socket *sock, int level, int optname, 
	case SO_RCVLOWAT:

		if (val < 0)

			val = INT_MAX;

		if (sock->ops->set_rcvlowat)

			ret = sock->ops->set_rcvlowat(sk, val);

		else

			sk->sk_rcvlowat = val ? : 1;

		break;

net/ipv4/af_inet.c

+1 −0
Original line number Diff line number Diff line
@@ -1006,6 +1006,7 @@ const struct proto_ops inet_stream_ops = { 
	.compat_getsockopt = compat_sock_common_getsockopt,

	.compat_ioctl	   = inet_compat_ioctl,

#endif

	.set_rcvlowat	   = tcp_set_rcvlowat,

};

EXPORT_SYMBOL(inet_stream_ops);

net/ipv4/tcp.c

+21 −0
Original line number Diff line number Diff line
@@ -1701,6 +1701,27 @@ int tcp_peek_len(struct socket *sock) 
}

EXPORT_SYMBOL(tcp_peek_len);



/* Make sure sk_rcvbuf is big enough to satisfy SO_RCVLOWAT hint */

int tcp_set_rcvlowat(struct sock *sk, int val)

{

	sk->sk_rcvlowat = val ? : 1;

	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)

		return 0;



	/* val comes from user space and might be close to INT_MAX */

	val <<= 1;

	if (val < 0)

		val = INT_MAX;



	val = min(val, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);

	if (val > sk->sk_rcvbuf) {

		sk->sk_rcvbuf = val;

		tcp_sk(sk)->window_clamp = tcp_win_from_space(sk, val);

	}

	return 0;

}

EXPORT_SYMBOL(tcp_set_rcvlowat);



static void tcp_update_recv_tstamps(struct sk_buff *skb,

				    struct scm_timestamping *tss)

{