ipv4: Namespaceify min_adv_mss sysctl knob

Different netns has different requirement on the setting of min_adv_mss
sysctl which the advertised MSS will be never lower than.

Enable min_adv_mss to be configured per network namespace.
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netns/ipv4.h

@@ -83,6 +83,7 @@ struct netns_ipv4 {
 
 	u32 ip_rt_min_pmtu;
 	int ip_rt_mtu_expires;
+	int ip_rt_min_advmss;
 
 	struct local_ports ip_local_ports;
 

net/ipv4/route.c

@@ -112,14 +112,13 @@
 
 #define DEFAULT_MIN_PMTU (512 + 20 + 20)
 #define DEFAULT_MTU_EXPIRES (10 * 60 * HZ)
-
+#define DEFAULT_MIN_ADVMSS 256
 static int ip_rt_max_size;
 static int ip_rt_redirect_number __read_mostly	= 9;
 static int ip_rt_redirect_load __read_mostly	= HZ / 50;
 static int ip_rt_redirect_silence __read_mostly	= ((HZ / 50) << (9 + 1));
 static int ip_rt_error_cost __read_mostly	= HZ;
 static int ip_rt_error_burst __read_mostly	= 5 * HZ;
-static int ip_rt_min_advmss __read_mostly	= 256;
 
 static int ip_rt_gc_timeout __read_mostly	= RT_GC_TIMEOUT;
 
@@ -1298,9 +1297,10 @@ static void set_class_tag(struct rtable *rt, u32 tag)
 
 static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
 {
+	struct net *net = dev_net(dst->dev);
 	unsigned int header_size = sizeof(struct tcphdr) + sizeof(struct iphdr);
 	unsigned int advmss = max_t(unsigned int, ipv4_mtu(dst) - header_size,
-				    ip_rt_min_advmss);
+				    net->ipv4.ip_rt_min_advmss);
 
 	return min(advmss, IPV4_MAX_PMTU - header_size);
 }
@@ -3535,13 +3535,6 @@ static struct ctl_table ipv4_route_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
-	{
-		.procname	= "min_adv_mss",
-		.data		= &ip_rt_min_advmss,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
 	{ }
 };
 
@@ -3569,6 +3562,13 @@ static struct ctl_table ipv4_route_netns_table[] = {
 		.mode           = 0644,
 		.proc_handler   = proc_dointvec_jiffies,
 	},
+	{
+		.procname   = "min_adv_mss",
+		.data       = &init_net.ipv4.ip_rt_min_advmss,
+		.maxlen     = sizeof(int),
+		.mode       = 0644,
+		.proc_handler   = proc_dointvec,
+	},
 	{ },
 };
 
@@ -3631,6 +3631,7 @@ static __net_init int netns_ip_rt_init(struct net *net)
 	/* Set default value for namespaceified sysctls */
 	net->ipv4.ip_rt_min_pmtu = DEFAULT_MIN_PMTU;
 	net->ipv4.ip_rt_mtu_expires = DEFAULT_MTU_EXPIRES;
+	net->ipv4.ip_rt_min_advmss = DEFAULT_MIN_ADVMSS;
 	return 0;
 }