[NET]: IP header modifier helpers annotations.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsfield.h

@@ -27,7 +27,7 @@ static inline __u8 ipv6_get_dsfield(struct ipv6hdr *ipv6h)
 static inline void ipv4_change_dsfield(struct iphdr *iph,__u8 mask,
     __u8 value)
 {
-        __u32 check = ntohs(iph->check);
+        __u32 check = ntohs((__force __be16)iph->check);
 	__u8 dsfield;
 
 	dsfield = (iph->tos & mask) | value;
@@ -35,7 +35,7 @@ static inline void ipv4_change_dsfield(struct iphdr *iph,__u8 mask,
 	if ((check+1) >> 16) check = (check+1) & 0xffff;
 	check -= dsfield;
 	check += check >> 16; /* adjust carry */
-	iph->check = htons(check);
+	iph->check = (__force __sum16)htons(check);
 	iph->tos = dsfield;
 }
 

include/net/inet_ecn.h

@@ -53,7 +53,7 @@ static inline __u8 INET_ECN_encapsulate(__u8 outer, __u8 inner)
 
 static inline int IP_ECN_set_ce(struct iphdr *iph)
 {
-	u32 check = iph->check;
+	u32 check = (__force u32)iph->check;
 	u32 ecn = (iph->tos + 1) & INET_ECN_MASK;
 
 	/*
@@ -71,9 +71,9 @@ static inline int IP_ECN_set_ce(struct iphdr *iph)
 	 * INET_ECN_ECT_1 => check += htons(0xFFFD)
 	 * INET_ECN_ECT_0 => check += htons(0xFFFE)
 	 */
-	check += htons(0xFFFB) + htons(ecn);
+	check += (__force u16)htons(0xFFFB) + (__force u16)htons(ecn);
 
-	iph->check = check + (check>=0xFFFF);
+	iph->check = (__force __sum16)(check + (check>=0xFFFF));
 	iph->tos |= INET_ECN_CE;
 	return 1;
 }

include/net/ip.h

@@ -192,9 +192,9 @@ extern void ipfrag_init(void);
 static inline
 int ip_decrease_ttl(struct iphdr *iph)
 {
-	u32 check = iph->check;
-	check += htons(0x0100);
-	iph->check = check + (check>=0xFFFF);
+	u32 check = (__force u32)iph->check;
+	check += (__force u32)htons(0x0100);
+	iph->check = (__force __sum16)(check + (check>=0xFFFF));
 	return --iph->ttl;
 }