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tcp: add tcp_mss_clamp() helper

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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>
This commit is contained in:
Eric Dumazet 2017-02-02 08:04:56 -08:00 • committed by David S. Miller
parent ff3edc9b8e
commit 3541f9e8bd
5 changed files with 17 additions and 23 deletions
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14
net/ipv4/tcp_output.c
View file

@ -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;