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-rw-r--r--include/linux/tcp.h9
1 files changed, 9 insertions, 0 deletions
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index f88f4649ba6f..cfc2d9506ce8 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 */