IPv6: add extack info for IPv6 address add/delete

Add extack info for IPv6 address add/delete, which would be useful for
users to understand the problem without having to read kernel code.
Suggested-by: Beniamino Galvani <bgalvani@redhat.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_route.h

@@ -156,7 +156,7 @@ void fib6_force_start_gc(struct net *net);
 
 struct fib6_info *addrconf_f6i_alloc(struct net *net, struct inet6_dev *idev,
 				     const struct in6_addr *addr, bool anycast,
-				     gfp_t gfp_flags);
+				     gfp_t gfp_flags, struct netlink_ext_ack *extack);
 
 struct rt6_info *ip6_dst_alloc(struct net *net, struct net_device *dev,
 			       int flags);

net/ipv6/addrconf.c

@@ -1063,20 +1063,28 @@ ipv6_add_addr(struct inet6_dev *idev, struct ifa6_config *cfg,
 	struct fib6_info *f6i = NULL;
 	int err = 0;
 
-	if (addr_type == IPV6_ADDR_ANY ||
-	    (addr_type & IPV6_ADDR_MULTICAST &&
-	     !(cfg->ifa_flags & IFA_F_MCAUTOJOIN)) ||
-	    (!(idev->dev->flags & IFF_LOOPBACK) &&
-	     !netif_is_l3_master(idev->dev) &&
-	     addr_type & IPV6_ADDR_LOOPBACK))
+	if (addr_type == IPV6_ADDR_ANY) {
+		NL_SET_ERR_MSG_MOD(extack, "Invalid address");
 		return ERR_PTR(-EADDRNOTAVAIL);
+	} else if (addr_type & IPV6_ADDR_MULTICAST &&
+		   !(cfg->ifa_flags & IFA_F_MCAUTOJOIN)) {
+		NL_SET_ERR_MSG_MOD(extack, "Cannot assign multicast address without \"IFA_F_MCAUTOJOIN\" flag");
+		return ERR_PTR(-EADDRNOTAVAIL);
+	} else if (!(idev->dev->flags & IFF_LOOPBACK) &&
+		   !netif_is_l3_master(idev->dev) &&
+		   addr_type & IPV6_ADDR_LOOPBACK) {
+		NL_SET_ERR_MSG_MOD(extack, "Cannot assign loopback address on this device");
+		return ERR_PTR(-EADDRNOTAVAIL);
+	}
 
 	if (idev->dead) {
-		err = -ENODEV;			/*XXX*/
+		NL_SET_ERR_MSG_MOD(extack, "device is going away");
+		err = -ENODEV;
 		goto out;
 	}
 
 	if (idev->cnf.disable_ipv6) {
+		NL_SET_ERR_MSG_MOD(extack, "IPv6 is disabled on this device");
 		err = -EACCES;
 		goto out;
 	}
@@ -1103,7 +1111,7 @@ ipv6_add_addr(struct inet6_dev *idev, struct ifa6_config *cfg,
 		goto out;
 	}
 
-	f6i = addrconf_f6i_alloc(net, idev, cfg->pfx, false, gfp_flags);
+	f6i = addrconf_f6i_alloc(net, idev, cfg->pfx, false, gfp_flags, extack);
 	if (IS_ERR(f6i)) {
 		err = PTR_ERR(f6i);
 		f6i = NULL;
@@ -2927,30 +2935,40 @@ static int inet6_addr_add(struct net *net, int ifindex,
 
 	ASSERT_RTNL();
 
-	if (cfg->plen > 128)
+	if (cfg->plen > 128) {
+		NL_SET_ERR_MSG_MOD(extack, "Invalid prefix length");
 		return -EINVAL;
+	}
 
 	/* check the lifetime */
-	if (!cfg->valid_lft || cfg->preferred_lft > cfg->valid_lft)
+	if (!cfg->valid_lft || cfg->preferred_lft > cfg->valid_lft) {
+		NL_SET_ERR_MSG_MOD(extack, "address lifetime invalid");
 		return -EINVAL;
+	}
 
-	if (cfg->ifa_flags & IFA_F_MANAGETEMPADDR && cfg->plen != 64)
+	if (cfg->ifa_flags & IFA_F_MANAGETEMPADDR && cfg->plen != 64) {
+		NL_SET_ERR_MSG_MOD(extack, "address with \"mngtmpaddr\" flag must have a prefix length of 64");
 		return -EINVAL;
+	}
 
 	dev = __dev_get_by_index(net, ifindex);
 	if (!dev)
 		return -ENODEV;
 
 	idev = addrconf_add_dev(dev);
-	if (IS_ERR(idev))
+	if (IS_ERR(idev)) {
+		NL_SET_ERR_MSG_MOD(extack, "IPv6 is disabled on this device");
 		return PTR_ERR(idev);
+	}
 
 	if (cfg->ifa_flags & IFA_F_MCAUTOJOIN) {
 		int ret = ipv6_mc_config(net->ipv6.mc_autojoin_sk,
 					 true, cfg->pfx, ifindex);
 
-		if (ret < 0)
+		if (ret < 0) {
+			NL_SET_ERR_MSG_MOD(extack, "Multicast auto join failed");
 			return ret;
+		}
 	}
 
 	cfg->scope = ipv6_addr_scope(cfg->pfx);
@@ -3007,22 +3025,29 @@ static int inet6_addr_add(struct net *net, int ifindex,
 }
 
 static int inet6_addr_del(struct net *net, int ifindex, u32 ifa_flags,
-			  const struct in6_addr *pfx, unsigned int plen)
+			  const struct in6_addr *pfx, unsigned int plen,
+			  struct netlink_ext_ack *extack)
 {
 	struct inet6_ifaddr *ifp;
 	struct inet6_dev *idev;
 	struct net_device *dev;
 
-	if (plen > 128)
+	if (plen > 128) {
+		NL_SET_ERR_MSG_MOD(extack, "Invalid prefix length");
 		return -EINVAL;
+	}
 
 	dev = __dev_get_by_index(net, ifindex);
-	if (!dev)
+	if (!dev) {
+		NL_SET_ERR_MSG_MOD(extack, "Unable to find the interface");
 		return -ENODEV;
+	}
 
 	idev = __in6_dev_get(dev);
-	if (!idev)
+	if (!idev) {
+		NL_SET_ERR_MSG_MOD(extack, "IPv6 is disabled on this device");
 		return -ENXIO;
+	}
 
 	read_lock_bh(&idev->lock);
 	list_for_each_entry(ifp, &idev->addr_list, if_list) {
@@ -3045,6 +3070,8 @@ static int inet6_addr_del(struct net *net, int ifindex, u32 ifa_flags,
 		}
 	}
 	read_unlock_bh(&idev->lock);
+
+	NL_SET_ERR_MSG_MOD(extack, "address not found");
 	return -EADDRNOTAVAIL;
 }
 
@@ -3087,7 +3114,7 @@ int addrconf_del_ifaddr(struct net *net, void __user *arg)
 
 	rtnl_lock();
 	err = inet6_addr_del(net, ireq.ifr6_ifindex, 0, &ireq.ifr6_addr,
-			     ireq.ifr6_prefixlen);
+			     ireq.ifr6_prefixlen, NULL);
 	rtnl_unlock();
 	return err;
 }
@@ -3490,7 +3517,7 @@ static int fixup_permanent_addr(struct net *net,
 		struct fib6_info *f6i, *prev;
 
 		f6i = addrconf_f6i_alloc(net, idev, &ifp->addr, false,
-					 GFP_ATOMIC);
+					 GFP_ATOMIC, NULL);
 		if (IS_ERR(f6i))
 			return PTR_ERR(f6i);
 
@@ -4700,7 +4727,7 @@ inet6_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh,
 	ifa_flags &= IFA_F_MANAGETEMPADDR;
 
 	return inet6_addr_del(net, ifm->ifa_index, ifa_flags, pfx,
-			      ifm->ifa_prefixlen);
+			      ifm->ifa_prefixlen, extack);
 }
 
 static int modify_prefix_route(struct inet6_ifaddr *ifp,
@@ -4905,8 +4932,10 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
 	}
 
 	dev =  __dev_get_by_index(net, ifm->ifa_index);
-	if (!dev)
+	if (!dev) {
+		NL_SET_ERR_MSG_MOD(extack, "Unable to find the interface");
 		return -ENODEV;
+	}
 
 	if (tb[IFA_FLAGS])
 		cfg.ifa_flags = nla_get_u32(tb[IFA_FLAGS]);
@@ -4941,10 +4970,12 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
 	}
 
 	if (nlh->nlmsg_flags & NLM_F_EXCL ||
-	    !(nlh->nlmsg_flags & NLM_F_REPLACE))
+	    !(nlh->nlmsg_flags & NLM_F_REPLACE)) {
+		NL_SET_ERR_MSG_MOD(extack, "address already assigned");
 		err = -EEXIST;
-	else
+	} else {
 		err = inet6_addr_modify(net, ifa, &cfg);
+	}
 
 	in6_ifa_put(ifa);
 

net/ipv6/anycast.c

@@ -305,7 +305,7 @@ int __ipv6_dev_ac_inc(struct inet6_dev *idev, const struct in6_addr *addr)
 	}
 
 	net = dev_net(idev->dev);
-	f6i = addrconf_f6i_alloc(net, idev, addr, true, GFP_ATOMIC);
+	f6i = addrconf_f6i_alloc(net, idev, addr, true, GFP_ATOMIC, NULL);
 	if (IS_ERR(f6i)) {
 		err = PTR_ERR(f6i);
 		goto out;

net/ipv6/route.c

@@ -4543,7 +4543,8 @@ static int ip6_pkt_prohibit_out(struct net *net, struct sock *sk, struct sk_buff
 struct fib6_info *addrconf_f6i_alloc(struct net *net,
 				     struct inet6_dev *idev,
 				     const struct in6_addr *addr,
-				     bool anycast, gfp_t gfp_flags)
+				     bool anycast, gfp_t gfp_flags,
+				     struct netlink_ext_ack *extack)
 {
 	struct fib6_config cfg = {
 		.fc_table = l3mdev_fib_table(idev->dev) ? : RT6_TABLE_LOCAL,
@@ -4565,7 +4566,7 @@ struct fib6_info *addrconf_f6i_alloc(struct net *net,
 		cfg.fc_flags |= RTF_LOCAL;
 	}
 
-	f6i = ip6_route_info_create(&cfg, gfp_flags, NULL);
+	f6i = ip6_route_info_create(&cfg, gfp_flags, extack);
 	if (!IS_ERR(f6i)) {
 		f6i->dst_nocount = true;