From d1361840f8c519eaee9a78ffe09e4f0a1b586846 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 16 Apr 2018 10:33:35 -0700 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- include/linux/net.h | 1 + include/net/tcp.h | 1 + net/core/sock.c | 5 ++++- net/ipv4/af_inet.c | 1 + net/ipv4/tcp.c | 21 +++++++++++++++++++++ net/ipv6/af_inet6.c | 1 + 6 files changed, 29 insertions(+), 1 deletion(-) diff --git a/include/linux/net.h b/include/linux/net.h index 2248a052061d..6554d3ba4396 100644 --- a/include/linux/net.h +++ b/include/linux/net.h @@ -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) \ diff --git a/include/net/tcp.h b/include/net/tcp.h index 9c9b3768b350..b2318242cad8 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -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); diff --git a/net/core/sock.c b/net/core/sock.c index 6444525f610c..b2c3db169ca1 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -905,7 +905,10 @@ set_rcvbuf: case SO_RCVLOWAT: if (val < 0) val = INT_MAX; - sk->sk_rcvlowat = val ? : 1; + if (sock->ops->set_rcvlowat) + ret = sock->ops->set_rcvlowat(sk, val); + else + sk->sk_rcvlowat = val ? : 1; break; case SO_RCVTIMEO: diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index eaed0367e669..f5c562aaef35 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -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); diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index bccc4c270087..0abd8d1d3d1d 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -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) { diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c index 8da0b513f188..e70d59fb26e1 100644 --- a/net/ipv6/af_inet6.c +++ b/net/ipv6/af_inet6.c @@ -590,6 +590,7 @@ const struct proto_ops inet6_stream_ops = { .compat_setsockopt = compat_sock_common_setsockopt, .compat_getsockopt = compat_sock_common_getsockopt, #endif + .set_rcvlowat = tcp_set_rcvlowat, }; const struct proto_ops inet6_dgram_ops = { -- 2.11.0