From: Yuyang Huang <yuyanghuang@google.com>
Date: Tue, 7 Jan 2025 11:43:55 +0000 (+0900)
Subject: netlink: add IPv6 anycast join/leave notifications
X-Git-Tag: v6.14-rc1~162^2~115
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=33d97a07b3ae6fa713919de4e1864ca04fff8f80;p=thirdparty%2Flinux.git

netlink: add IPv6 anycast join/leave notifications

This change introduces a mechanism for notifying userspace
applications about changes to IPv6 anycast addresses via netlink. It
includes:

* Addition and deletion of IPv6 anycast addresses are reported using
  RTM_NEWANYCAST and RTM_DELANYCAST.
* A new netlink group (RTNLGRP_IPV6_ACADDR) for subscribing to these
  notifications.

This enables user space applications(e.g. ip monitor) to efficiently
track anycast addresses through netlink messages, improving metrics
collection and system monitoring. It also unlocks the potential for
advanced anycast management in user space, such as hardware offload
control and fine grained network control.

Cc: Maciej Żenczykowski <maze@google.com>
Cc: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Yuyang Huang <yuyanghuang@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20250107114355.1766086-1-yuyanghuang@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---

diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 58337898fa21d..f8f91b2038eaf 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -546,4 +546,7 @@ int inet6_fill_ifmcaddr(struct sk_buff *skb,
 			const struct ifmcaddr6 *ifmca,
 			struct inet6_fill_args *args);
 
+int inet6_fill_ifacaddr(struct sk_buff *skb,
+			const struct ifacaddr6 *ifaca,
+			struct inet6_fill_args *args);
 #endif
diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index 5ee94c511a28a..66c3903d29cf6 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -100,7 +100,11 @@ enum {
 	RTM_GETMULTICAST,
 #define RTM_GETMULTICAST RTM_GETMULTICAST
 
-	RTM_GETANYCAST	= 62,
+	RTM_NEWANYCAST	= 60,
+#define RTM_NEWANYCAST RTM_NEWANYCAST
+	RTM_DELANYCAST,
+#define RTM_DELANYCAST RTM_DELANYCAST
+	RTM_GETANYCAST,
 #define RTM_GETANYCAST	RTM_GETANYCAST
 
 	RTM_NEWNEIGHTBL	= 64,
@@ -783,6 +787,8 @@ enum rtnetlink_groups {
 #define RTNLGRP_IPV4_MCADDR	RTNLGRP_IPV4_MCADDR
 	RTNLGRP_IPV6_MCADDR,
 #define RTNLGRP_IPV6_MCADDR	RTNLGRP_IPV6_MCADDR
+	RTNLGRP_IPV6_ACADDR,
+#define RTNLGRP_IPV6_ACADDR	RTNLGRP_IPV6_ACADDR
 	__RTNLGRP_MAX
 };
 #define RTNLGRP_MAX	(__RTNLGRP_MAX - 1)
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 4da409bc45777..c3729382be3bd 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5240,9 +5240,9 @@ int inet6_fill_ifmcaddr(struct sk_buff *skb,
 	return 0;
 }
 
-static int inet6_fill_ifacaddr(struct sk_buff *skb,
-			       const struct ifacaddr6 *ifaca,
-			       struct inet6_fill_args *args)
+int inet6_fill_ifacaddr(struct sk_buff *skb,
+			const struct ifacaddr6 *ifaca,
+			struct inet6_fill_args *args)
 {
 	struct net_device *dev = fib6_info_nh_dev(ifaca->aca_rt);
 	int ifindex = dev ? dev->ifindex : 1;
diff --git a/net/ipv6/anycast.c b/net/ipv6/anycast.c
index 562cace50ca9a..21e01695b48cd 100644
--- a/net/ipv6/anycast.c
+++ b/net/ipv6/anycast.c
@@ -278,6 +278,37 @@ static struct ifacaddr6 *aca_alloc(struct fib6_info *f6i,
 	return aca;
 }
 
+static void inet6_ifacaddr_notify(struct net_device *dev,
+				  const struct ifacaddr6 *ifaca, int event)
+{
+	struct inet6_fill_args fillargs = {
+		.event = event,
+		.netnsid = -1,
+	};
+	struct net *net = dev_net(dev);
+	struct sk_buff *skb;
+	int err = -ENOMEM;
+
+	skb = nlmsg_new(NLMSG_ALIGN(sizeof(struct ifaddrmsg)) +
+			nla_total_size(sizeof(struct in6_addr)) +
+			nla_total_size(sizeof(struct ifa_cacheinfo)),
+			GFP_KERNEL);
+	if (!skb)
+		goto error;
+
+	err = inet6_fill_ifacaddr(skb, ifaca, &fillargs);
+	if (err < 0) {
+		pr_err("Failed to fill in anycast addresses (err %d)\n", err);
+		nlmsg_free(skb);
+		goto error;
+	}
+
+	rtnl_notify(skb, net, 0, RTNLGRP_IPV6_ACADDR, NULL, GFP_KERNEL);
+	return;
+error:
+	rtnl_set_sk_err(net, RTNLGRP_IPV6_ACADDR, err);
+}
+
 /*
  *	device anycast group inc (add if not found)
  */
@@ -333,6 +364,8 @@ int __ipv6_dev_ac_inc(struct inet6_dev *idev, const struct in6_addr *addr)
 
 	addrconf_join_solict(idev->dev, &aca->aca_addr);
 
+	inet6_ifacaddr_notify(idev->dev, aca, RTM_NEWANYCAST);
+
 	aca_put(aca);
 	return 0;
 out:
@@ -375,6 +408,8 @@ int __ipv6_dev_ac_dec(struct inet6_dev *idev, const struct in6_addr *addr)
 
 	ip6_del_rt(dev_net(idev->dev), aca->aca_rt, false);
 
+	inet6_ifacaddr_notify(idev->dev, aca, RTM_DELANYCAST);
+
 	aca_put(aca);
 	return 0;
 }