sysctl net: Keep tcp_syn_retries inside the boundary

Limit the min/max value passed to the
/proc/sys/net/ipv4/tcp_syn_retries.
Signed-off-by: Michal Tesar <mtesar@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

(cherry picked from commit 651e9271)
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

net/ipv4/sysctl_net_ipv4.c

@@ -31,6 +31,8 @@ static int one = 1;
 static int two = 2;
 static int gso_max_segs = GSO_MAX_SEGS;
 static int tcp_retr1_max = 255;
+static int tcp_syn_retries_min = 1;
+static int tcp_syn_retries_max = MAX_TCP_SYNCNT;
 static int ip_local_port_range_min[] = { 1, 1 };
 static int ip_local_port_range_max[] = { 65535, 65535 };
 static int tcp_adv_win_scale_min = -31;
@@ -320,7 +322,9 @@ static struct ctl_table ipv4_table[] = {
 		.data		= &ipv4_config.no_pmtu_disc,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &tcp_syn_retries_min,
+		.extra2		= &tcp_syn_retries_max
 	},
 	{
 		.procname	= "ip_nonlocal_bind",