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| diff --git a/src/4.15.18/tcp_output.c b/src/4.15.18/tcp_output.c
index 82613f5..270545e 100644
--- a/src/4.15.18/tcp_output.c
+++ b/src/4.15.18/tcp_output.c
@@ -52,6 +52,7 @@
#include "fec_core.h"
u32 sysctl_post_local = 0xffffff00;
+int sysctl_mss_adjust = 0;
static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
int push_one, gfp_t gfp);
@@ -1720,6 +1721,8 @@ unsigned int tcp_current_mss(struct sock *sk)
mss_now = tcp_sync_mss(sk, mtu);
}
+ mss_now -= sysctl_mss_adjust;
+
header_len = tcp_established_options(sk, NULL, &opts, &md5, getconninfo(sk)) +
sizeof(struct tcphdr);
/* The mss_cache is sized based on tp->tcp_header_len, which assumes
@@ -3401,6 +3404,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
skb_dst_set(skb, dst);
mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
+ mss -= sysctl_mss_adjust;
memset(&opts, 0, sizeof(opts));
#ifdef CONFIG_SYN_COOKIES
@@ -3561,6 +3565,7 @@ static void tcp_connect_init(struct sock *sk)
if (!tp->window_clamp)
tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
+ tp->advmss -= sysctl_mss_adjust;
tcp_initialize_rcv_mss(sk);
diff --git a/src/io_sysctl.c b/src/io_sysctl.c
index c3b2ddd..6fdc1df 100644
--- a/src/io_sysctl.c
+++ b/src/io_sysctl.c
@@ -9,6 +9,7 @@ extern int sysctl_detail;
extern int sysctl_data_ssthresh;
extern int sysctl_post_local;
+extern int sysctl_mss_adjust;
extern unsigned long total_session;
extern unsigned long current_session;
@@ -39,6 +40,13 @@ static struct ctl_table tcp_sysctl_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec
},
+ {
+ .procname = "mss_adjust",
+ .data = &sysctl_mss_adjust,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec
+ },
{
.procname = "total_session",
.data = &total_session,
|
