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 f88f464..cfc2d95 100644
--- 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 8c9e9aa..8c124d4 100644
--- 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 bdb4434..dff7d2a 100644
--- 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 6d5bab8..956bea9 100644
--- 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 64834ec..6b9fc63 100644
--- 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);