net: Define IP flag field values

These defines were pulled from the "Add simple
IP/UDP fragmentation support" patch from Frank
Haverkamp <haver@vnet.ibm.com>.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>
diff --git a/net/net.c b/net/net.c
index 77e83b5..cf1f4fa 100644
--- a/net/net.c
+++ b/net/net.c
@@ -735,7 +735,7 @@
 	ip->ip_tos   = 0;
 	ip->ip_len   = htons(IP_HDR_SIZE_NO_UDP + 8);
 	ip->ip_id    = htons(NetIPID++);
-	ip->ip_off   = htons(0x4000);	/* No fragmentation */
+	ip->ip_off   = htons(IP_FLAGS_DFRAG);	/* Don't fragment */
 	ip->ip_ttl   = 255;
 	ip->ip_p     = 0x01;		/* ICMP */
 	ip->ip_sum   = 0;
@@ -1399,7 +1399,7 @@
 		if ((ip->ip_hl_v & 0xf0) != 0x40) {
 			return;
 		}
-		if (ip->ip_off & htons(0x1fff)) { /* Can't deal w/ fragments */
+		if (ip->ip_off & htons(IP_OFFS)) { /* Can't deal w/ fragments */
 			return;
 		}
 		/* can't deal with headers > 20 bytes */
@@ -1698,7 +1698,7 @@
 	ip->ip_tos   = 0;
 	ip->ip_len   = htons(IP_HDR_SIZE + len);
 	ip->ip_id    = htons(NetIPID++);
-	ip->ip_off   = htons(0x4000);	/* No fragmentation */
+	ip->ip_off   = htons(IP_FLAGS_DFRAG);	/* Don't fragment */
 	ip->ip_ttl   = 255;
 	ip->ip_p     = 17;		/* UDP */
 	ip->ip_sum   = 0;