[IPV6] Use macro for M-Flag and clean-up.

Use macro IP6_MF for the M-Flag.
Clean-up for readability (commented by <aj@dungeon.inka.de>).

include/net/ipv6.h

@@ -101,6 +101,8 @@ struct frag_hdr {
 	__u32		identification;
 };
 
+#define	IP6_MF	0x0001
+
 #ifdef __KERNEL__
 
 #include <net/sock.h>

net/ipv6/ip6_output.c

@@ -984,7 +984,7 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 		ipv6_select_ident(skb, fh);
 		fh->nexthdr = nexthdr;
 		fh->reserved = 0;
-		fh->frag_off = htons(0x0001);
+		fh->frag_off = htons(IP6_MF);
 		frag_id = fh->identification;
 
 		first_len = skb_pagelen(skb);
@@ -1004,7 +1004,9 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 				offset += skb->len - hlen - sizeof(struct frag_hdr);
 				fh->nexthdr = nexthdr;
 				fh->reserved = 0;
-				fh->frag_off = htons(offset | (frag->next != NULL ? 0x0001 : 0));
+				fh->frag_off = htons(offset);
+				if (frag->next != NULL)
+					fh->frag_off |= htons(IP6_MF);
 				fh->identification = frag_id;
 				frag->nh.ipv6h->payload_len = htons(frag->len - sizeof(struct ipv6hdr));
 				ip6_copy_metadata(frag, skb);
@@ -1111,7 +1113,9 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 			BUG();
 		left -= len;
 
-		fh->frag_off = htons( left > 0 ?  (offset | 0x0001) : offset);
+		fh->frag_off = htons(offset);
+		if (left > 0)
+			fh->frag_off |= htons(IP6_MF);
 		frag->nh.ipv6h->payload_len = htons(frag->len - sizeof(struct ipv6hdr));
 
 		ptr += len;

net/ipv6/reassembly.c

@@ -435,7 +435,7 @@ static void ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
  				     csum_partial(skb->nh.raw, (u8*)(fhdr+1)-skb->nh.raw, 0));
 
 	/* Is this the final fragment? */
-	if (!(fhdr->frag_off & htons(0x0001))) {
+	if (!(fhdr->frag_off & htons(IP6_MF))) {
 		/* If we already have some bits beyond end
 		 * or have different end, the segment is corrupted.
 		 */