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authorEric Dumazet <edumazet@google.com>2017-02-02 08:04:56 -0800
committerDavid S. Miller <davem@davemloft.net>2017-02-03 11:19:34 -0500
commit3541f9e8bdebce02458882b66b638d7302c1f616 (patch)
tree1049ef01f68f197e66fa77f18768aaf6d219f8b1 /include/linux/tcp.h
parentff3edc9b8efc8200c25f3a5adfb1c1de0a882dc5 (diff)
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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>
Diffstat (limited to 'include/linux/tcp.h')
-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 */