ipv6: introduce dst_rt6_info() helper

Instead of (struct rt6_info *)dst casts, we can use :

 #define dst_rt6_info(_ptr) \
         container_of_const(_ptr, struct rt6_info, dst)

Some places needed missing const qualifiers :

ip6_confirm_neigh(), ipv6_anycast_destination(),
ipv6_unicast_destination(), has_gateway()

v2: added missing parts (David Ahern)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/infiniband/core/addr.c

@@ -348,15 +348,15 @@ static int dst_fetch_ha(const struct dst_entry *dst,
 
 static bool has_gateway(const struct dst_entry *dst, sa_family_t family)
 {
-	struct rtable *rt;
-	struct rt6_info *rt6;
+	const struct rtable *rt;
+	const struct rt6_info *rt6;
 
 	if (family == AF_INET) {
 		rt = container_of(dst, struct rtable, dst);
 		return rt->rt_uses_gateway;
 	}
 
-	rt6 = container_of(dst, struct rt6_info, dst);
+	rt6 = dst_rt6_info(dst);
 	return rt6->rt6i_flags & RTF_GATEWAY;
 }
 

drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c

@@ -540,7 +540,7 @@ mlxsw_sp_span_gretap6_route(const struct net_device *to_dev,
 	if (!dst || dst->error)
 		goto out;
 
-	rt6 = container_of(dst, struct rt6_info, dst);
+	rt6 = dst_rt6_info(dst);
 
 	dev = dst->dev;
 	*saddrp = fl6.saddr;

drivers/net/vrf.c

@@ -653,7 +653,7 @@ static int vrf_finish_output6(struct net *net, struct sock *sk,
 	skb->dev = dev;
 
 	rcu_read_lock();
-	nexthop = rt6_nexthop((struct rt6_info *)dst, &ipv6_hdr(skb)->daddr);
+	nexthop = rt6_nexthop(dst_rt6_info(dst), &ipv6_hdr(skb)->daddr);
 	neigh = __ipv6_neigh_lookup_noref(dst->dev, nexthop);
 	if (unlikely(!neigh))
 		neigh = __neigh_create(&nd_tbl, nexthop, dst->dev, false);

drivers/net/vxlan/vxlan_core.c

@@ -2513,7 +2513,7 @@ void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 		}
 
 		if (!info) {
-			u32 rt6i_flags = ((struct rt6_info *)ndst)->rt6i_flags;
+			u32 rt6i_flags = dst_rt6_info(ndst)->rt6i_flags;
 
 			err = encap_bypass_if_local(skb, dev, vxlan, AF_INET6,
 						    dst_port, ifindex, vni,

drivers/s390/net/qeth_core.h

@@ -956,7 +956,7 @@ static inline struct dst_entry *qeth_dst_check_rcu(struct sk_buff *skb,
 	struct dst_entry *dst = skb_dst(skb);
 	struct rt6_info *rt;
 
-	rt = (struct rt6_info *) dst;
+	rt = dst_rt6_info(dst);
 	if (dst) {
 		if (proto == htons(ETH_P_IPV6))
 			dst = dst_check(dst, rt6_get_cookie(rt));
@@ -978,7 +978,7 @@ static inline __be32 qeth_next_hop_v4_rcu(struct sk_buff *skb,
 static inline struct in6_addr *qeth_next_hop_v6_rcu(struct sk_buff *skb,
 						    struct dst_entry *dst)
 {
-	struct rt6_info *rt = (struct rt6_info *) dst;
+	struct rt6_info *rt = dst_rt6_info(dst);
 
 	if (rt && !ipv6_addr_any(&rt->rt6i_gateway))
 		return &rt->rt6i_gateway;

include/net/ip6_fib.h

@@ -234,9 +234,11 @@ struct fib6_result {
 	for (rt = (w)->leaf; rt;					\
 	     rt = rcu_dereference_protected(rt->fib6_next, 1))
 
-static inline struct inet6_dev *ip6_dst_idev(struct dst_entry *dst)
+#define dst_rt6_info(_ptr) container_of_const(_ptr, struct rt6_info, dst)
+
+static inline struct inet6_dev *ip6_dst_idev(const struct dst_entry *dst)
 {
-	return ((struct rt6_info *)dst)->rt6i_idev;
+	return dst_rt6_info(dst)->rt6i_idev;
 }
 
 static inline bool fib6_requires_src(const struct fib6_info *rt)

include/net/ip6_route.h

@@ -210,12 +210,11 @@ void rt6_uncached_list_del(struct rt6_info *rt);
 static inline const struct rt6_info *skb_rt6_info(const struct sk_buff *skb)
 {
 	const struct dst_entry *dst = skb_dst(skb);
-	const struct rt6_info *rt6 = NULL;
 
 	if (dst)
-		rt6 = container_of(dst, struct rt6_info, dst);
+		return dst_rt6_info(dst);
 
-	return rt6;
+	return NULL;
 }
 
 /*
@@ -227,7 +226,7 @@ static inline void ip6_dst_store(struct sock *sk, struct dst_entry *dst,
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 
-	np->dst_cookie = rt6_get_cookie((struct rt6_info *)dst);
+	np->dst_cookie = rt6_get_cookie(dst_rt6_info(dst));
 	sk_setup_caps(sk, dst);
 	np->daddr_cache = daddr;
 #ifdef CONFIG_IPV6_SUBTREES
@@ -240,15 +239,15 @@ void ip6_sk_dst_store_flow(struct sock *sk, struct dst_entry *dst,
 
 static inline bool ipv6_unicast_destination(const struct sk_buff *skb)
 {
-	struct rt6_info *rt = (struct rt6_info *) skb_dst(skb);
+	const struct rt6_info *rt = dst_rt6_info(skb_dst(skb));
 
 	return rt->rt6i_flags & RTF_LOCAL;
 }
 
 static inline bool ipv6_anycast_destination(const struct dst_entry *dst,
 					    const struct in6_addr *daddr)
 {
-	struct rt6_info *rt = (struct rt6_info *)dst;
+	const struct rt6_info *rt = dst_rt6_info(dst);
 
 	return rt->rt6i_flags & RTF_ANYCAST ||
 		(rt->rt6i_dst.plen < 127 &&

net/bluetooth/6lowpan.c

@@ -133,7 +133,7 @@ static inline struct lowpan_peer *peer_lookup_dst(struct lowpan_btle_dev *dev,
 						  struct in6_addr *daddr,
 						  struct sk_buff *skb)
 {
-	struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
+	struct rt6_info *rt = dst_rt6_info(skb_dst(skb));
 	int count = atomic_read(&dev->peer_count);
 	const struct in6_addr *nexthop;
 	struct lowpan_peer *peer;

net/core/dst_cache.c

@@ -112,7 +112,7 @@ void dst_cache_set_ip6(struct dst_cache *dst_cache, struct dst_entry *dst,
 
 	idst = this_cpu_ptr(dst_cache->cache);
 	dst_cache_per_cpu_dst_set(this_cpu_ptr(dst_cache->cache), dst,
-				  rt6_get_cookie((struct rt6_info *)dst));
+				  rt6_get_cookie(dst_rt6_info(dst)));
 	idst->in6_saddr = *saddr;
 }
 EXPORT_SYMBOL_GPL(dst_cache_set_ip6);

net/core/filter.c

@@ -2215,7 +2215,7 @@ static int bpf_out_neigh_v6(struct net *net, struct sk_buff *skb,
 	rcu_read_lock();
 	if (!nh) {
 		dst = skb_dst(skb);
-		nexthop = rt6_nexthop(container_of(dst, struct rt6_info, dst),
+		nexthop = rt6_nexthop(dst_rt6_info(dst),
 				      &ipv6_hdr(skb)->daddr);
 	} else {
 		nexthop = &nh->ipv6_nh;

net/ipv4/ip_tunnel.c

@@ -543,7 +543,7 @@ static int tnl_update_pmtu(struct net_device *dev, struct sk_buff *skb,
 		struct rt6_info *rt6;
 		__be32 daddr;
 
-		rt6 = skb_valid_dst(skb) ? (struct rt6_info *)skb_dst(skb) :
+		rt6 = skb_valid_dst(skb) ? dst_rt6_info(skb_dst(skb)) :
 					   NULL;
 		daddr = md ? dst : tunnel->parms.iph.daddr;
 

net/ipv6/icmp.c

@@ -212,7 +212,7 @@ static bool icmpv6_xrlim_allow(struct sock *sk, u8 type,
 	} else if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) {
 		res = true;
 	} else {
-		struct rt6_info *rt = (struct rt6_info *)dst;
+		struct rt6_info *rt = dst_rt6_info(dst);
 		int tmo = net->ipv6.sysctl.icmpv6_time;
 		struct inet_peer *peer;
 
@@ -241,7 +241,7 @@ static bool icmpv6_rt_has_prefsrc(struct sock *sk, u8 type,
 
 	dst = ip6_route_output(net, sk, fl6);
 	if (!dst->error) {
-		struct rt6_info *rt = (struct rt6_info *)dst;
+		struct rt6_info *rt = dst_rt6_info(dst);
 		struct in6_addr prefsrc;
 
 		rt6_get_prefsrc(rt, &prefsrc);
@@ -616,7 +616,7 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 	if (ip6_append_data(sk, icmpv6_getfrag, &msg,
 			    len + sizeof(struct icmp6hdr),
 			    sizeof(struct icmp6hdr),
-			    &ipc6, &fl6, (struct rt6_info *)dst,
+			    &ipc6, &fl6, dst_rt6_info(dst),
 			    MSG_DONTWAIT)) {
 		ICMP6_INC_STATS(net, idev, ICMP6_MIB_OUTERRORS);
 		ip6_flush_pending_frames(sk);
@@ -803,7 +803,7 @@ static enum skb_drop_reason icmpv6_echo_reply(struct sk_buff *skb)
 	if (ip6_append_data(sk, icmpv6_getfrag, &msg,
 			    skb->len + sizeof(struct icmp6hdr),
 			    sizeof(struct icmp6hdr), &ipc6, &fl6,
-			    (struct rt6_info *)dst, MSG_DONTWAIT)) {
+			    dst_rt6_info(dst), MSG_DONTWAIT)) {
 		__ICMP6_INC_STATS(net, idev, ICMP6_MIB_OUTERRORS);
 		ip6_flush_pending_frames(sk);
 	} else {

net/ipv6/ila/ila_lwt.c

@@ -38,7 +38,7 @@ static inline struct ila_params *ila_params_lwtunnel(
 static int ila_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	struct dst_entry *orig_dst = skb_dst(skb);
-	struct rt6_info *rt = (struct rt6_info *)orig_dst;
+	struct rt6_info *rt = dst_rt6_info(orig_dst);
 	struct ila_lwt *ilwt = ila_lwt_lwtunnel(orig_dst->lwtstate);
 	struct dst_entry *dst;
 	int err = -EINVAL;
@@ -70,7 +70,7 @@ static int ila_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 		memset(&fl6, 0, sizeof(fl6));
 		fl6.flowi6_oif = orig_dst->dev->ifindex;
 		fl6.flowi6_iif = LOOPBACK_IFINDEX;
-		fl6.daddr = *rt6_nexthop((struct rt6_info *)orig_dst,
+		fl6.daddr = *rt6_nexthop(dst_rt6_info(orig_dst),
 					 &ip6h->daddr);
 
 		dst = ip6_route_output(net, NULL, &fl6);

net/ipv6/ip6_output.c

@@ -120,7 +120,7 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *
 	IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_OUT, skb->len);
 
 	rcu_read_lock();
-	nexthop = rt6_nexthop((struct rt6_info *)dst, daddr);
+	nexthop = rt6_nexthop(dst_rt6_info(dst), daddr);
 	neigh = __ipv6_neigh_lookup_noref(dev, nexthop);
 
 	if (unlikely(IS_ERR_OR_NULL(neigh))) {
@@ -599,7 +599,7 @@ int ip6_forward(struct sk_buff *skb)
 		 *	send a redirect.
 		 */
 
-		rt = (struct rt6_info *) dst;
+		rt = dst_rt6_info(dst);
 		if (rt->rt6i_flags & RTF_GATEWAY)
 			target = &rt->rt6i_gateway;
 		else
@@ -856,7 +856,7 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 		 int (*output)(struct net *, struct sock *, struct sk_buff *))
 {
 	struct sk_buff *frag;
-	struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
+	struct rt6_info *rt = dst_rt6_info(skb_dst(skb));
 	struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?
 				inet6_sk(skb->sk) : NULL;
 	bool mono_delivery_time = skb->mono_delivery_time;
@@ -1063,7 +1063,7 @@ static struct dst_entry *ip6_sk_dst_check(struct sock *sk,
 		return NULL;
 	}
 
-	rt = (struct rt6_info *)dst;
+	rt = dst_rt6_info(dst);
 	/* Yes, checking route validity in not connected
 	 * case is not very simple. Take into account,
 	 * that we do not support routing by source, TOS,
@@ -1118,7 +1118,7 @@ static int ip6_dst_lookup_tail(struct net *net, const struct sock *sk,
 		struct rt6_info *rt;
 
 		*dst = ip6_route_output(net, sk, fl6);
-		rt = (*dst)->error ? NULL : (struct rt6_info *)*dst;
+		rt = (*dst)->error ? NULL : dst_rt6_info(*dst);
 
 		rcu_read_lock();
 		from = rt ? rcu_dereference(rt->from) : NULL;
@@ -1159,7 +1159,7 @@ static int ip6_dst_lookup_tail(struct net *net, const struct sock *sk,
 	 * dst entry and replace it instead with the
 	 * dst entry of the nexthop router
 	 */
-	rt = (struct rt6_info *) *dst;
+	rt = dst_rt6_info(*dst);
 	rcu_read_lock();
 	n = __ipv6_neigh_lookup_noref(rt->dst.dev,
 				      rt6_nexthop(rt, &fl6->daddr));
@@ -1423,7 +1423,7 @@ static int __ip6_append_data(struct sock *sk,
 	int offset = 0;
 	bool zc = false;
 	u32 tskey = 0;
-	struct rt6_info *rt = (struct rt6_info *)cork->dst;
+	struct rt6_info *rt = dst_rt6_info(cork->dst);
 	bool paged, hold_tskey, extra_uref = false;
 	struct ipv6_txoptions *opt = v6_cork->opt;
 	int csummode = CHECKSUM_NONE;
@@ -1877,7 +1877,7 @@ struct sk_buff *__ip6_make_skb(struct sock *sk,
 	struct net *net = sock_net(sk);
 	struct ipv6hdr *hdr;
 	struct ipv6_txoptions *opt = v6_cork->opt;
-	struct rt6_info *rt = (struct rt6_info *)cork->base.dst;
+	struct rt6_info *rt = dst_rt6_info(cork->base.dst);
 	struct flowi6 *fl6 = &cork->fl.u.ip6;
 	unsigned char proto = fl6->flowi6_proto;
 
@@ -1949,7 +1949,7 @@ struct sk_buff *__ip6_make_skb(struct sock *sk,
 int ip6_send_skb(struct sk_buff *skb)
 {
 	struct net *net = sock_net(skb->sk);
-	struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
+	struct rt6_info *rt = dst_rt6_info(skb_dst(skb));
 	int err;
 
 	err = ip6_local_out(net, skb->sk, skb);

net/ipv6/ip6mr.c

@@ -2273,7 +2273,7 @@ int ip6mr_get_route(struct net *net, struct sk_buff *skb, struct rtmsg *rtm,
 	int err;
 	struct mr_table *mrt;
 	struct mfc6_cache *cache;
-	struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
+	struct rt6_info *rt = dst_rt6_info(skb_dst(skb));
 
 	mrt = ip6mr_get_table(net, RT6_TABLE_DFLT);
 	if (!mrt)

net/ipv6/ndisc.c

@@ -1722,7 +1722,7 @@ void ndisc_send_redirect(struct sk_buff *skb, const struct in6_addr *target)
 	if (IS_ERR(dst))
 		return;
 
-	rt = (struct rt6_info *) dst;
+	rt = dst_rt6_info(dst);
 
 	if (rt->rt6i_flags & RTF_GATEWAY) {
 		ND_PRINTK(2, warn,

net/ipv6/ping.c

@@ -154,7 +154,7 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	dst = ip6_sk_dst_lookup_flow(sk, &fl6, daddr, false);
 	if (IS_ERR(dst))
 		return PTR_ERR(dst);
-	rt = (struct rt6_info *) dst;
+	rt = dst_rt6_info(dst);
 
 	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
 		fl6.flowi6_oif = READ_ONCE(np->mcast_oif);

net/ipv6/raw.c

@@ -598,7 +598,7 @@ static int rawv6_send_hdrinc(struct sock *sk, struct msghdr *msg, int length,
 	struct ipv6hdr *iph;
 	struct sk_buff *skb;
 	int err;
-	struct rt6_info *rt = (struct rt6_info *)*dstp;
+	struct rt6_info *rt = dst_rt6_info(*dstp);
 	int hlen = LL_RESERVED_SPACE(rt->dst.dev);
 	int tlen = rt->dst.dev->needed_tailroom;
 
@@ -917,7 +917,7 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		ipc6.opt = opt;
 		lock_sock(sk);
 		err = ip6_append_data(sk, raw6_getfrag, &rfv,
-			len, 0, &ipc6, &fl6, (struct rt6_info *)dst,
+			len, 0, &ipc6, &fl6, dst_rt6_info(dst),
 			msg->msg_flags);
 
 		if (err)