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: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -197,6 +197,7 @@ struct proto_ops {
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int offset, size_t size, int flags);
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int (*sendmsg_locked)(struct sock *sk, struct msghdr *msg,
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size_t size);
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int (*set_rcvlowat)(struct sock *sk, int val);
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};
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#define DECLARE_SOCKADDR(type, dst, src) \
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@ -402,6 +402,7 @@ void tcp_set_keepalive(struct sock *sk, int val);
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void tcp_syn_ack_timeout(const struct request_sock *req);
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int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
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int flags, int *addr_len);
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int tcp_set_rcvlowat(struct sock *sk, int val);
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void tcp_parse_options(const struct net *net, const struct sk_buff *skb,
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struct tcp_options_received *opt_rx,
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int estab, struct tcp_fastopen_cookie *foc);
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@ -905,7 +905,10 @@ set_rcvbuf:
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case SO_RCVLOWAT:
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if (val < 0)
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val = INT_MAX;
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sk->sk_rcvlowat = val ? : 1;
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if (sock->ops->set_rcvlowat)
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ret = sock->ops->set_rcvlowat(sk, val);
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else
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sk->sk_rcvlowat = val ? : 1;
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break;
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case SO_RCVTIMEO:
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@ -1006,6 +1006,7 @@ const struct proto_ops inet_stream_ops = {
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.compat_getsockopt = compat_sock_common_getsockopt,
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.compat_ioctl = inet_compat_ioctl,
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#endif
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.set_rcvlowat = tcp_set_rcvlowat,
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};
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EXPORT_SYMBOL(inet_stream_ops);
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@ -1701,6 +1701,27 @@ int tcp_peek_len(struct socket *sock)
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}
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EXPORT_SYMBOL(tcp_peek_len);
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/* Make sure sk_rcvbuf is big enough to satisfy SO_RCVLOWAT hint */
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int tcp_set_rcvlowat(struct sock *sk, int val)
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{
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sk->sk_rcvlowat = val ? : 1;
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if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)
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return 0;
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/* val comes from user space and might be close to INT_MAX */
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val <<= 1;
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if (val < 0)
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val = INT_MAX;
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val = min(val, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
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if (val > sk->sk_rcvbuf) {
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sk->sk_rcvbuf = val;
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tcp_sk(sk)->window_clamp = tcp_win_from_space(sk, val);
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}
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return 0;
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}
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EXPORT_SYMBOL(tcp_set_rcvlowat);
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static void tcp_update_recv_tstamps(struct sk_buff *skb,
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struct scm_timestamping *tss)
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{
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@ -590,6 +590,7 @@ const struct proto_ops inet6_stream_ops = {
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.compat_setsockopt = compat_sock_common_setsockopt,
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.compat_getsockopt = compat_sock_common_getsockopt,
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#endif
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.set_rcvlowat = tcp_set_rcvlowat,
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};
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const struct proto_ops inet6_dgram_ops = {
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