inet: constify ip headers and in6_addr

Add const qualifiers to structs iphdr, ipv6hdr and in6_addr pointers
where possible, to make code intention more obvious.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

64 files changed, 316 insertions, 310 deletions

diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 23710aa6a18..7c4d92c0dd1 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -61,16 +61,16 @@ extern int			addrconf_set_dstaddr(struct net *net,
 						     void __user *arg);
 
 extern int			ipv6_chk_addr(struct net *net,
-					      struct in6_addr *addr,
+					      const struct in6_addr *addr,
 					      struct net_device *dev,
 					      int strict);
 
 #if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 extern int			ipv6_chk_home_addr(struct net *net,
-						   struct in6_addr *addr);
+						   const struct in6_addr *addr);
 #endif
 
-extern int			ipv6_chk_prefix(struct in6_addr *addr,
+extern int			ipv6_chk_prefix(const struct in6_addr *addr,
 						struct net_device *dev);
 
 extern struct inet6_ifaddr      *ipv6_get_ifaddr(struct net *net,
@@ -89,9 +89,9 @@ extern int			ipv6_get_lladdr(struct net_device *dev,
 extern int 			ipv6_rcv_saddr_equal(const struct sock *sk,
 						    const struct sock *sk2);
 extern void			addrconf_join_solict(struct net_device *dev,
-					struct in6_addr *addr);
+					const struct in6_addr *addr);
 extern void			addrconf_leave_solict(struct inet6_dev *idev,
-					struct in6_addr *addr);
+					const struct in6_addr *addr);
 
 static inline unsigned long addrconf_timeout_fixup(u32 timeout,
 						    unsigned unit)
@@ -158,15 +158,15 @@ extern void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len);
 /*
  *	anycast prototypes (anycast.c)
  */
-extern int ipv6_sock_ac_join(struct sock *sk,int ifindex,struct in6_addr *addr);
-extern int ipv6_sock_ac_drop(struct sock *sk,int ifindex,struct in6_addr *addr);
+extern int ipv6_sock_ac_join(struct sock *sk,int ifindex, const struct in6_addr *addr);
+extern int ipv6_sock_ac_drop(struct sock *sk,int ifindex, const struct in6_addr *addr);
 extern void ipv6_sock_ac_close(struct sock *sk);
-extern int inet6_ac_check(struct sock *sk, struct in6_addr *addr, int ifindex);
+extern int inet6_ac_check(struct sock *sk, const struct in6_addr *addr, int ifindex);
 
-extern int ipv6_dev_ac_inc(struct net_device *dev, struct in6_addr *addr);
-extern int __ipv6_dev_ac_dec(struct inet6_dev *idev, struct in6_addr *addr);
+extern int ipv6_dev_ac_inc(struct net_device *dev, const struct in6_addr *addr);
+extern int __ipv6_dev_ac_dec(struct inet6_dev *idev, const struct in6_addr *addr);
 extern int ipv6_chk_acast_addr(struct net *net, struct net_device *dev,
-			       struct in6_addr *addr);
+			       const struct in6_addr *addr);
 
 
 /* Device notifier */
diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index fccc2180c61..3d982f72d48 100644
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h
@@ -196,7 +196,7 @@ struct inet6_dev {
 	struct rcu_head		rcu;
 };
 
-static inline void ipv6_eth_mc_map(struct in6_addr *addr, char *buf)
+static inline void ipv6_eth_mc_map(const struct in6_addr *addr, char *buf)
 {
 	/*
 	 *	+-------+-------+-------+-------+-------+-------+
@@ -210,7 +210,7 @@ static inline void ipv6_eth_mc_map(struct in6_addr *addr, char *buf)
 	memcpy(buf + 2, &addr->s6_addr32[3], sizeof(__u32));
 }
 
-static inline void ipv6_tr_mc_map(struct in6_addr *addr, char *buf)
+static inline void ipv6_tr_mc_map(const struct in6_addr *addr, char *buf)
 {
 	/* All nodes FF01::1, FF02::1, FF02::1:FFxx:xxxx */
 
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index e6dd8da6b2a..8a159cc3d68 100644
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -80,7 +80,7 @@ static inline struct inet_peer *inet_getpeer_v4(__be32 v4daddr, int create)
 	return inet_getpeer(&daddr, create);
 }
 
-static inline struct inet_peer *inet_getpeer_v6(struct in6_addr *v6daddr, int create)
+static inline struct inet_peer *inet_getpeer_v6(const struct in6_addr *v6daddr, int create)
 {
 	struct inetpeer_addr daddr;
 
diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 98348d53b2b..aca8ef4dd67 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -198,12 +198,12 @@ extern struct dst_entry         *fib6_rule_lookup(struct net *net,
 						  pol_lookup_t lookup);
 
 extern struct fib6_node		*fib6_lookup(struct fib6_node *root,
-					     struct in6_addr *daddr,
-					     struct in6_addr *saddr);
+					     const struct in6_addr *daddr,
+					     const struct in6_addr *saddr);
 
 struct fib6_node		*fib6_locate(struct fib6_node *root,
-					     struct in6_addr *daddr, int dst_len,
-					     struct in6_addr *saddr, int src_len);
+					     const struct in6_addr *daddr, int dst_len,
+					     const struct in6_addr *saddr, int src_len);
 
 extern void			fib6_clean_all(struct net *net,
 					       int (*func)(struct rt6_info *, void *arg),
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 86b1cb48690..d5c21d4d9e7 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -86,7 +86,7 @@ extern int			ip6_del_rt(struct rt6_info *);
 
 extern int			ip6_route_get_saddr(struct net *net,
 						    struct rt6_info *rt,
-						    struct in6_addr *daddr,
+						    const struct in6_addr *daddr,
 						    unsigned int prefs,
 						    struct in6_addr *saddr);
 
@@ -112,9 +112,9 @@ extern int			ip6_dst_hoplimit(struct dst_entry *dst);
  *	support functions for ND
  *
  */
-extern struct rt6_info *	rt6_get_dflt_router(struct in6_addr *addr,
+extern struct rt6_info *	rt6_get_dflt_router(const struct in6_addr *addr,
 						    struct net_device *dev);
-extern struct rt6_info *	rt6_add_dflt_router(struct in6_addr *gwaddr,
+extern struct rt6_info *	rt6_add_dflt_router(const struct in6_addr *gwaddr,
 						    struct net_device *dev,
 						    unsigned int pref);
 
@@ -122,17 +122,17 @@ extern void			rt6_purge_dflt_routers(struct net *net);
 
 extern int			rt6_route_rcv(struct net_device *dev,
 					      u8 *opt, int len,
-					      struct in6_addr *gwaddr);
+					      const struct in6_addr *gwaddr);
 
-extern void			rt6_redirect(struct in6_addr *dest,
-					     struct in6_addr *src,
-					     struct in6_addr *saddr,
+extern void			rt6_redirect(const struct in6_addr *dest,
+					     const struct in6_addr *src,
+					     const struct in6_addr *saddr,
 					     struct neighbour *neigh,
 					     u8 *lladdr,
 					     int on_link);
 
-extern void			rt6_pmtu_discovery(struct in6_addr *daddr,
-						   struct in6_addr *saddr,
+extern void			rt6_pmtu_discovery(const struct in6_addr *daddr,
+						   const struct in6_addr *saddr,
 						   struct net_device *dev,
 						   u32 pmtu);
 
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 34200f9e680..5da19265315 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -376,8 +376,8 @@ enum ip6_defrag_users {
 struct ip6_create_arg {
 	__be32 id;
 	u32 user;
-	struct in6_addr *src;
-	struct in6_addr *dst;
+	const struct in6_addr *src;
+	const struct in6_addr *dst;
 };
 
 void ip6_frag_init(struct inet_frag_queue *q, void *a);
diff --git a/include/net/ndisc.h b/include/net/ndisc.h
index e0e594f8e9d..6144685d601 100644
--- a/include/net/ndisc.h
+++ b/include/net/ndisc.h
@@ -102,7 +102,8 @@ extern void			ndisc_send_redirect(struct sk_buff *skb,
 						    struct neighbour *neigh,
 						    const struct in6_addr *target);
 
-extern int			ndisc_mc_map(struct in6_addr *addr, char *buf, struct net_device *dev, int dir);
+extern int			ndisc_mc_map(const struct in6_addr *addr, char *buf,
+					     struct net_device *dev, int dir);
 
 extern struct sk_buff		*ndisc_build_skb(struct net_device *dev,
 						 const struct in6_addr *daddr,
diff --git a/include/net/route.h b/include/net/route.h
index 3782cddd138..b3962e249e1 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -191,7 +191,8 @@ static inline int ip_route_input_noref(struct sk_buff *skb, __be32 dst, __be32 s
 	return ip_route_input_common(skb, dst, src, tos, devin, true);
 }
 
-extern unsigned short	ip_rt_frag_needed(struct net *net, struct iphdr *iph, unsigned short new_mtu, struct net_device *dev);
+extern unsigned short	ip_rt_frag_needed(struct net *net, const struct iphdr *iph,
+					  unsigned short new_mtu, struct net_device *dev);
 extern void		ip_rt_send_redirect(struct sk_buff *skb);
 
 extern unsigned		inet_addr_type(struct net *net, __be32 addr);
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 65ea3134863..1cdd4b7b286 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1475,7 +1475,7 @@ extern int xfrm6_input_addr(struct sk_buff *skb, xfrm_address_t *daddr,
 extern int xfrm6_tunnel_register(struct xfrm6_tunnel *handler, unsigned short family);
 extern int xfrm6_tunnel_deregister(struct xfrm6_tunnel *handler, unsigned short family);
 extern __be32 xfrm6_tunnel_alloc_spi(struct net *net, xfrm_address_t *saddr);
-extern __be32 xfrm6_tunnel_spi_lookup(struct net *net, xfrm_address_t *saddr);
+extern __be32 xfrm6_tunnel_spi_lookup(struct net *net, const xfrm_address_t *saddr);
 extern int xfrm6_extract_output(struct xfrm_state *x, struct sk_buff *skb);
 extern int xfrm6_prepare_output(struct xfrm_state *x, struct sk_buff *skb);
 extern int xfrm6_output(struct sk_buff *skb);
@@ -1569,8 +1569,8 @@ static inline int xfrm_addr_cmp(const xfrm_address_t *a,
 	case AF_INET:
 		return (__force u32)a->a4 - (__force u32)b->a4;
 	case AF_INET6:
-		return ipv6_addr_cmp((struct in6_addr *)a,
-				     (struct in6_addr *)b);
+		return ipv6_addr_cmp((const struct in6_addr *)a,
+				     (const struct in6_addr *)b);
 	}
 }
 
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 59660c909a7..2f14eafdeea 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -413,7 +413,7 @@ out:
 
 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 static struct sk_buff *br_ip6_multicast_alloc_query(struct net_bridge *br,
-						    struct in6_addr *group)
+						    const struct in6_addr *group)
 {
 	struct sk_buff *skb;
 	struct ipv6hdr *ip6h;
@@ -1115,7 +1115,7 @@ static int br_ip4_multicast_query(struct net_bridge *br,
 				  struct net_bridge_port *port,
 				  struct sk_buff *skb)
 {
-	struct iphdr *iph = ip_hdr(skb);
+	const struct iphdr *iph = ip_hdr(skb);
 	struct igmphdr *ih = igmp_hdr(skb);
 	struct net_bridge_mdb_entry *mp;
 	struct igmpv3_query *ih3;
@@ -1190,7 +1190,7 @@ static int br_ip6_multicast_query(struct net_bridge *br,
 				  struct net_bridge_port *port,
 				  struct sk_buff *skb)
 {
-	struct ipv6hdr *ip6h = ipv6_hdr(skb);
+	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 	struct mld_msg *mld = (struct mld_msg *) icmp6_hdr(skb);
 	struct net_bridge_mdb_entry *mp;
 	struct mld2_query *mld2q;
@@ -1198,7 +1198,7 @@ static int br_ip6_multicast_query(struct net_bridge *br,
 	struct net_bridge_port_group __rcu **pp;
 	unsigned long max_delay;
 	unsigned long now = jiffies;
-	struct in6_addr *group = NULL;
+	const struct in6_addr *group = NULL;
 	int err = 0;
 
 	spin_lock(&br->multicast_lock);
@@ -1356,7 +1356,7 @@ static int br_multicast_ipv4_rcv(struct net_bridge *br,
 				 struct sk_buff *skb)
 {
 	struct sk_buff *skb2 = skb;
-	struct iphdr *iph;
+	const struct iphdr *iph;
 	struct igmphdr *ih;
 	unsigned len;
 	unsigned offset;
@@ -1452,7 +1452,7 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
 				 struct sk_buff *skb)
 {
 	struct sk_buff *skb2;
-	struct ipv6hdr *ip6h;
+	const struct ipv6hdr *ip6h;
 	struct icmp6hdr *icmp6h;
 	u8 nexthdr;
 	unsigned len;
diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index f3bc322c589..5614907525e 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -219,7 +219,7 @@ static inline void nf_bridge_update_protocol(struct sk_buff *skb)
 static int br_parse_ip_options(struct sk_buff *skb)
 {
 	struct ip_options *opt;
-	struct iphdr *iph;
+	const struct iphdr *iph;
 	struct net_device *dev = skb->dev;
 	u32 len;
 
@@ -554,7 +554,7 @@ static unsigned int br_nf_pre_routing_ipv6(unsigned int hook,
 					   const struct net_device *out,
 					   int (*okfn)(struct sk_buff *))
 {
-	struct ipv6hdr *hdr;
+	const struct ipv6hdr *hdr;
 	u32 pkt_len;
 
 	if (skb->len < sizeof(struct ipv6hdr))
diff --git a/net/core/dev.c b/net/core/dev.c
index 3871bf69a38..379c993ff42 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2502,8 +2502,8 @@ static inline void ____napi_schedule(struct softnet_data *sd,
 __u32 __skb_get_rxhash(struct sk_buff *skb)
 {
 	int nhoff, hash = 0, poff;
-	struct ipv6hdr *ip6;
-	struct iphdr *ip;
+	const struct ipv6hdr *ip6;
+	const struct iphdr *ip;
 	u8 ip_proto;
 	u32 addr1, addr2, ihl;
 	union {
@@ -2518,7 +2518,7 @@ __u32 __skb_get_rxhash(struct sk_buff *skb)
 		if (!pskb_may_pull(skb, sizeof(*ip) + nhoff))
 			goto done;
 
-		ip = (struct iphdr *) (skb->data + nhoff);
+		ip = (const struct iphdr *) (skb->data + nhoff);
 		if (ip->frag_off & htons(IP_MF | IP_OFFSET))
 			ip_proto = 0;
 		else
@@ -2531,7 +2531,7 @@ __u32 __skb_get_rxhash(struct sk_buff *skb)
 		if (!pskb_may_pull(skb, sizeof(*ip6) + nhoff))
 			goto done;
 
-		ip6 = (struct ipv6hdr *) (skb->data + nhoff);
+		ip6 = (const struct ipv6hdr *) (skb->data + nhoff);
 		ip_proto = ip6->nexthdr;
 		addr1 = (__force u32) ip6->saddr.s6_addr32[3];
 		addr2 = (__force u32) ip6->daddr.s6_addr32[3];
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 06be2431753..46d9c3a4de2 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -539,7 +539,7 @@ int __netpoll_rx(struct sk_buff *skb)
 {
 	int proto, len, ulen;
 	int hits = 0;
-	struct iphdr *iph;
+	const struct iphdr *iph;
 	struct udphdr *uh;
 	struct netpoll_info *npinfo = skb->dev->npinfo;
 	struct netpoll *np, *tmp;
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index de1b7e37ad5..73add237324 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -54,8 +54,8 @@ static void dccp_v6_hash(struct sock *sk)
 
 /* add pseudo-header to DCCP checksum stored in skb->csum */
 static inline __sum16 dccp_v6_csum_finish(struct sk_buff *skb,
-				      struct in6_addr *saddr,
-				      struct in6_addr *daddr)
+				      const struct in6_addr *saddr,
+				      const struct in6_addr *daddr)
 {
 	return csum_ipv6_magic(saddr, daddr, skb->len, IPPROTO_DCCP, skb->csum);
 }
@@ -87,7 +87,7 @@ static inline __u32 dccp_v6_init_sequence(struct sk_buff *skb)
 static void dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 			u8 type, u8 code, int offset, __be32 info)
 {
-	struct ipv6hdr *hdr = (struct ipv6hdr *)skb->data;
+	const struct ipv6hdr *hdr = (const struct ipv6hdr *)skb->data;
 	const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data + offset);
 	struct dccp_sock *dp;
 	struct ipv6_pinfo *np;
@@ -296,7 +296,7 @@ static void dccp_v6_reqsk_destructor(struct request_sock *req)
 
 static void dccp_v6_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
 {
-	struct ipv6hdr *rxip6h;
+	const struct ipv6hdr *rxip6h;
 	struct sk_buff *skb;
 	struct flowi6 fl6;
 	struct net *net = dev_net(skb_dst(rxskb)->dev);
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 807d83c02ef..cae75ef21fe 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1186,7 +1186,7 @@ EXPORT_SYMBOL(inet_sk_rebuild_header);
 
 static int inet_gso_send_check(struct sk_buff *skb)
 {
-	struct iphdr *iph;
+	const struct iphdr *iph;
 	const struct net_protocol *ops;
 	int proto;
 	int ihl;
@@ -1293,7 +1293,7 @@ static struct sk_buff **inet_gro_receive(struct sk_buff **head,
 	const struct net_protocol *ops;
 	struct sk_buff **pp = NULL;
 	struct sk_buff *p;
-	struct iphdr *iph;
+	const struct iphdr *iph;
 	unsigned int hlen;
 	unsigned int off;
 	unsigned int id;
diff --git a/net/ipv4/ah4.c b/net/ipv4/ah4.c
index 4286fd3cc0e..c1f4154552f 100644
--- a/net/ipv4/ah4.c
+++ b/net/ipv4/ah4.c
@@ -73,7 +73,7 @@ static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
  * into IP header for icv calculation. Options are already checked
  * for validity, so paranoia is not required. */
 
-static int ip_clear_mutable_options(struct iphdr *iph, __be32 *daddr)
+static int ip_clear_mutable_options(const struct iphdr *iph, __be32 *daddr)
 {
 	unsigned char * optptr = (unsigned char*)(iph+1);
 	int  l = iph->ihl*4 - sizeof(struct iphdr);
@@ -396,7 +396,7 @@ out:
 static void ah4_err(struct sk_buff *skb, u32 info)
 {
 	struct net *net = dev_net(skb->dev);
-	struct iphdr *iph = (struct iphdr *)skb->data;
+	const struct iphdr *iph = (const struct iphdr *)skb->data;
 	struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
 	struct xfrm_state *x;
 
@@ -404,7 +404,8 @@ static void ah4_err(struct sk_buff *skb, u32 info)
 	    icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 		return;
 
-	x = xfrm_state_lookup(net, skb->mark, (xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
+	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
+			      ah->spi, IPPROTO_AH, AF_INET);
 	if (!x)
 		return;
 	printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 03f994bcf7d..a5b413416da 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -276,7 +276,7 @@ error:
 
 static int esp_input_done2(struct sk_buff *skb, int err)
 {
-	struct iphdr *iph;
+	const struct iphdr *iph;
 	struct xfrm_state *x = xfrm_input_state(skb);
 	struct esp_data *esp = x->data;
 	struct crypto_aead *aead = esp->aead;
@@ -484,7 +484,7 @@ static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
 static void esp4_err(struct sk_buff *skb, u32 info)
 {
 	struct net *net = dev_net(skb->dev);
-	struct iphdr *iph = (struct iphdr *)skb->data;
+	const struct iphdr *iph = (const struct iphdr *)skb->data;
 	struct ip_esp_hdr *esph = (struct ip_esp_hdr *)(skb->data+(iph->ihl<<2));
 	struct xfrm_state *x;
 
@@ -492,7 +492,8 @@ static void esp4_err(struct sk_buff *skb, u32 info)
 	    icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 		return;
 
-	x = xfrm_state_lookup(net, skb->mark, (xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
+	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
+			      esph->spi, IPPROTO_ESP, AF_INET);
 	if (!x)
 		return;
 	NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index e5f8a71d3a2..74e35e5736e 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -373,7 +373,7 @@ out_unlock:
 }
 
 static struct rtable *icmp_route_lookup(struct net *net, struct sk_buff *skb_in,
-					struct iphdr *iph,
+					const struct iphdr *iph,
 					__be32 saddr, u8 tos,
 					int type, int code,
 					struct icmp_bxm *param)
@@ -637,7 +637,7 @@ EXPORT_SYMBOL(icmp_send);
 
 static void icmp_unreach(struct sk_buff *skb)
 {
-	struct iphdr *iph;
+	const struct iphdr *iph;
 	struct icmphdr *icmph;
 	int hash, protocol;
 	const struct net_protocol *ipprot;
@@ -656,7 +656,7 @@ static void icmp_unreach(struct sk_buff *skb)
 		goto out_err;
 
 	icmph = icmp_hdr(skb);
-	iph   = (struct iphdr *)skb->data;
+	iph   = (const struct iphdr *)skb->data;
 
 	if (iph->ihl < 5) /* Mangled header, drop. */
 		goto out_err;
@@ -729,7 +729,7 @@ static void icmp_unreach(struct sk_buff *skb)
 	if (!pskb_may_pull(skb, iph->ihl * 4 + 8))
 		goto out;
 
-	iph = (struct iphdr *)skb->data;
+	iph = (const struct iphdr *)skb->data;
 	protocol = iph->protocol;
 
 	/*
@@ -758,7 +758,7 @@ out_err:
 
 static void icmp_redirect(struct sk_buff *skb)
 {
-	struct