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 @@
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 */