ipv4: Namespaceify tcp_max_syn_backlog knob

Different namespace application might require different maximal
number of remembered connection requests.

Signed-off-by: Haishuang Yan <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/netns/ipv4.h

···
 	unsigned int sysctl_tcp_notsent_lowat;
 	int sysctl_tcp_tw_reuse;
 	struct inet_timewait_death_row tcp_death_row;
+	int sysctl_max_syn_backlog;
 
 	int sysctl_igmp_max_memberships;
 	int sysctl_igmp_max_msf;

include/net/request_sock.h

···
 /*
  * NET		Generic infrastructure for Network protocols.
  *
- *		Definitions for request_sock 
+ *		Definitions for request_sock
  *
  * Authors:	Arnaldo Carvalho de Melo <[e-mail]>
  *
···
 	if (atomic_dec_and_test(&req->rsk_refcnt))
 		reqsk_free(req);
 }
-
-extern int sysctl_max_syn_backlog;
 
 /*
  * For a TCP Fast Open listener -

net/core/request_sock.c

···
  * and it will increase in proportion to the memory of machine.
  * Note : Dont forget somaxconn that may limit backlog too.
  */
-int sysctl_max_syn_backlog = 256;
-EXPORT_SYMBOL(sysctl_max_syn_backlog);
 
 void reqsk_queue_alloc(struct request_sock_queue *queue)
 {

net/ipv4/sysctl_net_ipv4.c

···
 		.proc_handler	= proc_dointvec
 	},
 	{
-		.procname	= "tcp_max_syn_backlog",
-		.data		= &sysctl_max_syn_backlog,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec
-	},
-	{
 		.procname	= "inet_peer_threshold",
 		.data		= &inet_peer_threshold,
 		.maxlen		= sizeof(int),
···
 	{
 		.procname	= "tcp_tw_recycle",
 		.data		= &init_net.ipv4.tcp_death_row.sysctl_tw_recycle,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec
+	},
+	{
+		.procname	= "tcp_max_syn_backlog",
+		.data		= &init_net.ipv4.sysctl_max_syn_backlog,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec

net/ipv4/tcp.c

···
 
 
 	cnt = tcp_hashinfo.ehash_mask + 1;
-
 	sysctl_tcp_max_orphans = cnt / 2;
-	sysctl_max_syn_backlog = max(128, cnt / 256);
 
 	tcp_init_mem();
 	/* Set per-socket limits to no more than 1/128 the pressure threshold */

net/ipv4/tcp_input.c

···
 		}
 		/* Kill the following clause, if you dislike this way. */
 		else if (!net->ipv4.sysctl_tcp_syncookies &&
-			 (sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
-			  (sysctl_max_syn_backlog >> 2)) &&
+			 (net->ipv4.sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
+			  (net->ipv4.sysctl_max_syn_backlog >> 2)) &&
 			 !tcp_peer_is_proven(req, dst, false,
 					     tmp_opt.saw_tstamp)) {
 			/* Without syncookies last quarter of

net/ipv4/tcp_ipv4.c

···
 
 static int __net_init tcp_sk_init(struct net *net)
 {
-	int res, cpu;
+	int res, cpu, cnt;
 
 	net->ipv4.tcp_sk = alloc_percpu(struct sock *);
 	if (!net->ipv4.tcp_sk)
···
 	net->ipv4.sysctl_tcp_notsent_lowat = UINT_MAX;
 	net->ipv4.sysctl_tcp_tw_reuse = 0;
 
+	cnt = tcp_hashinfo.ehash_mask + 1;
 	net->ipv4.tcp_death_row.sysctl_tw_recycle = 0;
-	net->ipv4.tcp_death_row.sysctl_max_tw_buckets = (tcp_hashinfo.ehash_mask + 1) / 2;
+	net->ipv4.tcp_death_row.sysctl_max_tw_buckets = (cnt + 1) / 2;
 	net->ipv4.tcp_death_row.hashinfo = &tcp_hashinfo;
+
+	net->ipv4.sysctl_max_syn_backlog = max(128, cnt / 256);
 
 	return 0;
 fail: