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/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 *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 @@
}
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 @@
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 @@
* 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;