net - IP_NODEFRAG option for IPv4 socket

this patch is implementing IP_NODEFRAG option for IPv4 socket.
The reason is, there's no other way to send out the packet with user
customized header of the reassembly part.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index d99e7e0..b4c0969 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -355,6 +355,8 @@
 	inet = inet_sk(sk);
 	inet->is_icsk = (INET_PROTOSW_ICSK & answer_flags) != 0;
 
+	inet->nodefrag = 0;
+
 	if (SOCK_RAW == sock->type) {
 		inet->inet_num = protocol;
 		if (IPPROTO_RAW == protocol)