tcp: add tcp_mss_clamp() helper

Small cleanup factorizing code doing the TCP_MAXSEG clamping.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index f88f4649ba6f8a9a19578f55272533a12e5c9680..cfc2d9506ce8077af1ec92eb7086fd52ce4fe1ac 100644 (file)
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -445,4 +445,13 @@ static inline void tcp_saved_syn_free(struct tcp_sock *tp)
 
 struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk);
 
+static inline u16 tcp_mss_clamp(const struct tcp_sock *tp, u16 mss)
+{
+       /* We use READ_ONCE() here because socket might not be locked.
+        * This happens for listeners.
+        */
+       u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);
+
+       return (user_mss && user_mss < mss) ? user_mss : mss;
+}
 #endif /* _LINUX_TCP_H */

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 8c9e9aa17d660d7e92bdced72ace0c8644621371..8c124d4ef4b72eb18df3fb2515ee141df9a521f3 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1324,10 +1324,7 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
        tcp_ca_openreq_child(newsk, dst);
 
        tcp_sync_mss(newsk, dst_mtu(dst));
-       newtp->advmss = dst_metric_advmss(dst);
-       if (tcp_sk(sk)->rx_opt.user_mss &&
-           tcp_sk(sk)->rx_opt.user_mss < newtp->advmss)
-               newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;
+       newtp->advmss = tcp_mss_clamp(tcp_sk(sk), dst_metric_advmss(dst));
 
        tcp_initialize_rcv_mss(newsk);
 

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index bdb443471c3914cd57c3836c43f73648b452c01e..dff7d2aaf8611e96da094097e1e153541b3e0119 100644 (file)
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -360,15 +360,12 @@ void tcp_openreq_init_rwin(struct request_sock *req,
 {
        struct inet_request_sock *ireq = inet_rsk(req);
        const struct tcp_sock *tp = tcp_sk(sk_listener);
-       u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);
        int full_space = tcp_full_space(sk_listener);
-       int mss = dst_metric_advmss(dst);
        u32 window_clamp;
        __u8 rcv_wscale;
+       int mss;
 
-       if (user_mss && user_mss < mss)
-               mss = user_mss;
-
+       mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
        window_clamp = READ_ONCE(tp->window_clamp);
        /* Set this up on the first call only */
        req->rsk_window_clamp = window_clamp ? : dst_metric(dst, RTAX_WINDOW);

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 6d5bab8a3ea65dc01e9d9363bf9164b9b3a00f4a..956bea9a5394f5c564f9903c478fa520fcd16f41 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3062,7 +3062,6 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
        struct sk_buff *skb;
        int tcp_header_size;
        struct tcphdr *th;
-       u16 user_mss;
        int mss;
 
        skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
@@ -3092,10 +3091,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
        }
        skb_dst_set(skb, dst);
 
-       mss = dst_metric_advmss(dst);
-       user_mss = READ_ONCE(tp->rx_opt.user_mss);
-       if (user_mss && user_mss < mss)
-               mss = user_mss;
+       mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
 
        memset(&opts, 0, sizeof(opts));
 #ifdef CONFIG_SYN_COOKIES
@@ -3201,9 +3197,7 @@ static void tcp_connect_init(struct sock *sk)
 
        if (!tp->window_clamp)
                tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
-       tp->advmss = dst_metric_advmss(dst);
-       if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)
-               tp->advmss = tp->rx_opt.user_mss;
+       tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
 
        tcp_initialize_rcv_mss(sk);
 
@@ -3280,8 +3274,8 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
         * user-MSS. Reserve maximum option space for middleboxes that add
         * private TCP options. The cost is reduced data space in SYN :(
         */
-       if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp)
-               tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
+       tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp);
+
        space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
                MAX_TCP_OPTION_SPACE;
 

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 64834ec5ab730a8d2b1828028432ddf9ac77714c..6b9fc63fd4d23f17a6716b3557098e09f4f1d439 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1147,10 +1147,7 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
        tcp_ca_openreq_child(newsk, dst);
 
        tcp_sync_mss(newsk, dst_mtu(dst));
-       newtp->advmss = dst_metric_advmss(dst);
-       if (tcp_sk(sk)->rx_opt.user_mss &&
-           tcp_sk(sk)->rx_opt.user_mss < newtp->advmss)
-               newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;
+       newtp->advmss = tcp_mss_clamp(tcp_sk(sk), dst_metric_advmss(dst));
 
        tcp_initialize_rcv_mss(newsk);