[NET]: Treat the sign of the result of skb_headroom() consistently

In some places, the result of skb_headroom() is compared to an unsigned
integer, and in others, the result is compared to a signed integer.  Make
the comparisons consistent and correct.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -994,7 +994,7 @@ static inline int pskb_may_pull(struct sk_buff *skb, unsigned int len)
  *
  *	Return the number of bytes of free space at the head of an &sk_buff.
  */
-static inline int skb_headroom(const struct sk_buff *skb)
+static inline unsigned int skb_headroom(const struct sk_buff *skb)
 {
 	return skb->data - skb->head;
 }
@@ -1347,7 +1347,7 @@ static inline struct sk_buff *netdev_alloc_skb(struct net_device *dev,
  *	Returns true if modifying the header part of the cloned buffer
  *	does not requires the data to be copied.
  */
-static inline int skb_clone_writable(struct sk_buff *skb, int len)
+static inline int skb_clone_writable(struct sk_buff *skb, unsigned int len)
 {
 	return !skb_header_cloned(skb) &&
 	       skb_headroom(skb) + len <= skb->hdr_len;

net/ipv4/ip_gre.c

@@ -674,7 +674,7 @@ static int ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	struct rtable *rt;     			/* Route to the other host */
 	struct net_device *tdev;			/* Device to other host */
 	struct iphdr  *iph;			/* Our new IP header */
-	int    max_headroom;			/* The extra header space needed */
+	unsigned int max_headroom;		/* The extra header space needed */
 	int    gre_hlen;
 	__be32 dst;
 	int    mtu;

net/ipv4/ip_output.c

@@ -161,7 +161,7 @@ static inline int ip_finish_output2(struct sk_buff *skb)
 	struct dst_entry *dst = skb->dst;
 	struct rtable *rt = (struct rtable *)dst;
 	struct net_device *dev = dst->dev;
-	int hh_len = LL_RESERVED_SPACE(dev);
+	unsigned int hh_len = LL_RESERVED_SPACE(dev);
 
 	if (rt->rt_type == RTN_MULTICAST)
 		IP_INC_STATS(IPSTATS_MIB_OUTMCASTPKTS);

net/ipv4/ipip.c

@@ -515,7 +515,7 @@ static int ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	struct net_device *tdev;			/* Device to other host */
 	struct iphdr  *old_iph = ip_hdr(skb);
 	struct iphdr  *iph;			/* Our new IP header */
-	int    max_headroom;			/* The extra header space needed */
+	unsigned int max_headroom;		/* The extra header space needed */
 	__be32 dst = tiph->daddr;
 	int    mtu;
 

net/ipv4/ipvs/ip_vs_xmit.c

@@ -325,7 +325,7 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 	__be16 df = old_iph->frag_off;
 	sk_buff_data_t old_transport_header = skb->transport_header;
 	struct iphdr  *iph;			/* Our new IP header */
-	int    max_headroom;			/* The extra header space needed */
+	unsigned int max_headroom;		/* The extra header space needed */
 	int    mtu;
 
 	EnterFunction(10);

net/ipv4/tcp_input.c

@@ -3909,7 +3909,7 @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list,
 
 	while (before(start, end)) {
 		struct sk_buff *nskb;
-		int header = skb_headroom(skb);
+		unsigned int header = skb_headroom(skb);
 		int copy = SKB_MAX_ORDER(header, 0);
 
 		/* Too big header? This can happen with IPv6. */

net/ipv6/ip6_output.c

@@ -171,7 +171,7 @@ int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
 	u32 mtu;
 
 	if (opt) {
-		int head_room;
+		unsigned int head_room;
 
 		/* First: exthdrs may take lots of space (~8K for now)
 		   MAX_HEADER is not enough.

net/ipv6/ip6_tunnel.c

@@ -838,7 +838,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
 	struct dst_entry *dst;
 	struct net_device *tdev;
 	int mtu;
-	int max_headroom = sizeof(struct ipv6hdr);
+	unsigned int max_headroom = sizeof(struct ipv6hdr);
 	u8 proto;
 	int err = -1;
 	int pkt_len;

net/ipv6/sit.c

@@ -430,7 +430,7 @@ static int ipip6_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	struct rtable *rt;     			/* Route to the other host */
 	struct net_device *tdev;			/* Device to other host */
 	struct iphdr  *iph;			/* Our new IP header */
-	int    max_headroom;			/* The extra header space needed */
+	unsigned int max_headroom;		/* The extra header space needed */
 	__be32 dst = tiph->daddr;
 	int    mtu;
 	struct in6_addr *addr6;