net: Add new protocol attribute to IP addresses

This patch adds a new protocol attribute to IPv4 and IPv6 addresses.
Inspiration was taken from the protocol attribute of routes. User space
applications like iproute2 can set/get the protocol with the Netlink API.

The attribute is stored as an 8-bit unsigned integer.

The protocol attribute is set by kernel for these categories:

- IPv4 and IPv6 loopback addresses
- IPv6 addresses generated from router announcements
- IPv6 link local addresses

User space may pass custom protocols, not defined by the kernel.

Grouping addresses on their origin is useful in scenarios where you want
to distinguish between addresses based on who added them, e.g. kernel
vs. user space.

Tagging addresses with a string label is an existing feature that could be
used as a solution. Unfortunately the max length of a label is
15 characters, and for compatibility reasons the label must be prefixed
with the name of the device followed by a colon. Since device names also
have a max length of 15 characters, only -1 characters is guaranteed to be
available for any origin tag, which is not that much.

A reference implementation of user space setting and getting protocols
is available for iproute2:

https://github.com/westermo/iproute2/commit/9a6ea18bd79f47f293e5edc7780f315ea42ff540

Signed-off-by: Jacques de Laval <Jacques.De.Laval@westermo.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20220217150202.80802-1-Jacques.De.Laval@westermo.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 21 insertions, 6 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 2f307da17f21..85bab3a35709 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1115,6 +1115,7 @@ ipv6_add_addr(struct inet6_dev *idev, struct ifa6_config *cfg,
 	ifa->prefix_len = cfg->plen;
 	ifa->rt_priority = cfg->rt_priority;
 	ifa->flags = cfg->ifa_flags;
+	ifa->ifa_proto = cfg->ifa_proto;
 	/* No need to add the TENTATIVE flag for addresses with NODAD */
 	if (!(cfg->ifa_flags & IFA_F_NODAD))
 		ifa->flags |= IFA_F_TENTATIVE;
@@ -2593,6 +2594,7 @@ int addrconf_prefix_rcv_add_addr(struct net *net, struct net_device *dev,
 			.valid_lft = valid_lft,
 			.preferred_lft = prefered_lft,
 			.scope = addr_type & IPV6_ADDR_SCOPE_MASK,
+			.ifa_proto = IFAPROT_KERNEL_RA
 		};
 
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
@@ -3077,7 +3079,7 @@ int addrconf_del_ifaddr(struct net *net, void __user *arg)
 }
 
 static void add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
-		     int plen, int scope)
+		     int plen, int scope, u8 proto)
 {
 	struct inet6_ifaddr *ifp;
 	struct ifa6_config cfg = {
@@ -3086,7 +3088,8 @@ static void add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
 		.ifa_flags = IFA_F_PERMANENT,
 		.valid_lft = INFINITY_LIFE_TIME,
 		.preferred_lft = INFINITY_LIFE_TIME,
-		.scope = scope
+		.scope = scope,
+		.ifa_proto = proto
 	};
 
 	ifp = ipv6_add_addr(idev, &cfg, true, NULL);
@@ -3131,7 +3134,7 @@ static void add_v4_addrs(struct inet6_dev *idev)
 	}
 
 	if (addr.s6_addr32[3]) {
-		add_addr(idev, &addr, plen, scope);
+		add_addr(idev, &addr, plen, scope, IFAPROT_UNSPEC);
 		addrconf_prefix_route(&addr, plen, 0, idev->dev, 0, pflags,
 				      GFP_KERNEL);
 		return;
@@ -3154,7 +3157,8 @@ static void add_v4_addrs(struct inet6_dev *idev)
 					flag |= IFA_HOST;
 				}
 
-				add_addr(idev, &addr, plen, flag);
+				add_addr(idev, &addr, plen, flag,
+					 IFAPROT_UNSPEC);
 				addrconf_prefix_route(&addr, plen, 0, idev->dev,
 						      0, pflags, GFP_KERNEL);
 			}
@@ -3177,7 +3181,7 @@ static void init_loopback(struct net_device *dev)
 		return;
 	}
 
-	add_addr(idev, &in6addr_loopback, 128, IFA_HOST);
+	add_addr(idev, &in6addr_loopback, 128, IFA_HOST, IFAPROT_KERNEL_LO);
 }
 
 void addrconf_add_linklocal(struct inet6_dev *idev,
@@ -3189,7 +3193,8 @@ void addrconf_add_linklocal(struct inet6_dev *idev,
 		.ifa_flags = flags | IFA_F_PERMANENT,
 		.valid_lft = INFINITY_LIFE_TIME,
 		.preferred_lft = INFINITY_LIFE_TIME,
-		.scope = IFA_LINK
+		.scope = IFA_LINK,
+		.ifa_proto = IFAPROT_KERNEL_LL
 	};
 	struct inet6_ifaddr *ifp;
 
@@ -4627,6 +4632,7 @@ static const struct nla_policy ifa_ipv6_policy[IFA_MAX+1] = {
 	[IFA_FLAGS]		= { .len = sizeof(u32) },
 	[IFA_RT_PRIORITY]	= { .len = sizeof(u32) },
 	[IFA_TARGET_NETNSID]	= { .type = NLA_S32 },
+	[IFA_PROTO]		= { .type = NLA_U8 },
 };
 
 static int
@@ -4752,6 +4758,7 @@ static int inet6_addr_modify(struct net *net, struct inet6_ifaddr *ifp,
 	ifp->tstamp = jiffies;
 	ifp->valid_lft = cfg->valid_lft;
 	ifp->prefered_lft = cfg->preferred_lft;
+	ifp->ifa_proto = cfg->ifa_proto;
 
 	if (cfg->rt_priority && cfg->rt_priority != ifp->rt_priority)
 		ifp->rt_priority = cfg->rt_priority;
@@ -4845,6 +4852,9 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (tb[IFA_RT_PRIORITY])
 		cfg.rt_priority = nla_get_u32(tb[IFA_RT_PRIORITY]);
 
+	if (tb[IFA_PROTO])
+		cfg.ifa_proto = nla_get_u8(tb[IFA_PROTO]);
+
 	cfg.valid_lft = INFINITY_LIFE_TIME;
 	cfg.preferred_lft = INFINITY_LIFE_TIME;
 
@@ -4948,6 +4958,7 @@ static inline int inet6_ifaddr_msgsize(void)
 	       + nla_total_size(16) /* IFA_ADDRESS */
 	       + nla_total_size(sizeof(struct ifa_cacheinfo))
 	       + nla_total_size(4)  /* IFA_FLAGS */
+	       + nla_total_size(1)  /* IFA_PROTO */
 	       + nla_total_size(4)  /* IFA_RT_PRIORITY */;
 }
 
@@ -5025,6 +5036,10 @@ static int inet6_fill_ifaddr(struct sk_buff *skb, struct inet6_ifaddr *ifa,
 	if (nla_put_u32(skb, IFA_FLAGS, ifa->flags) < 0)
 		goto error;
 
+	if (ifa->ifa_proto &&
+	    nla_put_u8(skb, IFA_PROTO, ifa->ifa_proto))
+		goto error;
+
 	nlmsg_end(skb, nlh);
 	return 0;