netlink: add IGMP/MLD join/leave notifications

This change introduces netlink notifications for multicast address
changes. The following features are included:
* Addition and deletion of multicast addresses are reported using
  RTM_NEWMULTICAST and RTM_DELMULTICAST messages with AF_INET and
  AF_INET6.
* Two new notification groups: RTNLGRP_IPV4_MCADDR and
  RTNLGRP_IPV6_MCADDR are introduced for receiving these events.

This change allows user space applications (e.g., ip monitor) to
efficiently track multicast group memberships by listening for netlink
events. Previously, applications relied on inefficient polling of
procfs, introducing delays. With netlink notifications, applications
receive realtime updates on multicast group membership changes,
enabling more precise metrics collection and system monitoring. 

This change also unlocks the potential for implementing a wide range
of sophisticated multicast related features in user space by allowing
applications to combine kernel provided multicast address information
with user space data and communicate decisions back to the kernel for
more fine grained control. This mechanism can be used for various
purposes, including multicast filtering, IGMP/MLD offload, and
IGMP/MLD snooping.

Cc: Maciej Żenczykowski <maze@google.com>
Cc: Lorenzo Colitti <lorenzo@google.com>
Co-developed-by: Patrick Ruddy <pruddy@vyatta.att-mail.com>
Signed-off-by: Patrick Ruddy <pruddy@vyatta.att-mail.com>
Link: https://lore.kernel.org/r/20180906091056.21109-1-pruddy@vyatta.att-mail.com
Signed-off-by: Yuyang Huang <yuyanghuang@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/igmp.h b/include/linux/igmp.h
index 5171231f70a8b35e5633dc2185f57f7d6ae0ccd1..073b30a9b8508fabc5fe25d507c9302eaf6c3f19 100644 (file)
--- a/include/linux/igmp.h
+++ b/include/linux/igmp.h
@@ -87,6 +87,8 @@ struct ip_mc_list {
        char                    loaded;
        unsigned char           gsquery;        /* check source marks? */
        unsigned char           crcount;
+       unsigned long           mca_cstamp;
+       unsigned long           mca_tstamp;
        struct rcu_head         rcu;
 };
 

diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 363dd63babe72f67f2b494bcf7fc0fd5153c6f3a..58337898fa21d5e72666c88c8feb81f61a780997 100644 (file)
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -88,6 +88,23 @@ struct ifa6_config {
        u16                     scope;
 };
 
+enum addr_type_t {
+       UNICAST_ADDR,
+       MULTICAST_ADDR,
+       ANYCAST_ADDR,
+};
+
+struct inet6_fill_args {
+       u32 portid;
+       u32 seq;
+       int event;
+       unsigned int flags;
+       int netnsid;
+       int ifindex;
+       enum addr_type_t type;
+       bool force_rt_scope_universe;
+};
+
 int addrconf_init(void);
 void addrconf_cleanup(void);
 
@@ -525,4 +542,8 @@ int if6_proc_init(void);
 void if6_proc_exit(void);
 #endif
 
+int inet6_fill_ifmcaddr(struct sk_buff *skb,
+                       const struct ifmcaddr6 *ifmca,
+                       struct inet6_fill_args *args);
+
 #endif

diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index db7254d52d9355f03ffc0b6cd76731554f0b1139..eccc0e7dcb7dbc4382fcebb9f4bc444d9792b2fa 100644 (file)
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -93,7 +93,11 @@ enum {
        RTM_NEWPREFIX   = 52,
 #define RTM_NEWPREFIX  RTM_NEWPREFIX
 
-       RTM_GETMULTICAST = 58,
+       RTM_NEWMULTICAST = 56,
+#define RTM_NEWMULTICAST RTM_NEWMULTICAST
+       RTM_DELMULTICAST,
+#define RTM_DELMULTICAST RTM_DELMULTICAST
+       RTM_GETMULTICAST,
 #define RTM_GETMULTICAST RTM_GETMULTICAST
 
        RTM_GETANYCAST  = 62,
@@ -774,6 +778,10 @@ enum rtnetlink_groups {
 #define RTNLGRP_TUNNEL         RTNLGRP_TUNNEL
        RTNLGRP_STATS,
 #define RTNLGRP_STATS          RTNLGRP_STATS
+       RTNLGRP_IPV4_MCADDR,
+#define RTNLGRP_IPV4_MCADDR    RTNLGRP_IPV4_MCADDR
+       RTNLGRP_IPV6_MCADDR,
+#define RTNLGRP_IPV6_MCADDR    RTNLGRP_IPV6_MCADDR
        __RTNLGRP_MAX
 };
 #define RTNLGRP_MAX    (__RTNLGRP_MAX - 1)

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 6a238398acc9d5684ec3d6305ef2a74834f5a3b3..8a370ef37d3f6d0ea96280a75667f292637fbdf6 100644 (file)
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -88,6 +88,8 @@
 #include <linux/byteorder/generic.h>
 
 #include <net/net_namespace.h>
+#include <net/netlink.h>
+#include <net/addrconf.h>
 #include <net/arp.h>
 #include <net/ip.h>
 #include <net/protocol.h>
@@ -1430,6 +1432,63 @@ static void ip_mc_hash_remove(struct in_device *in_dev,
        *mc_hash = im->next_hash;
 }
 
+static int inet_fill_ifmcaddr(struct sk_buff *skb, struct net_device *dev,
+                             const struct ip_mc_list *im, int event)
+{
+       struct ifa_cacheinfo ci;
+       struct ifaddrmsg *ifm;
+       struct nlmsghdr *nlh;
+
+       nlh = nlmsg_put(skb, 0, 0, event, sizeof(struct ifaddrmsg), 0);
+       if (!nlh)
+               return -EMSGSIZE;
+
+       ifm = nlmsg_data(nlh);
+       ifm->ifa_family = AF_INET;
+       ifm->ifa_prefixlen = 32;
+       ifm->ifa_flags = IFA_F_PERMANENT;
+       ifm->ifa_scope = RT_SCOPE_UNIVERSE;
+       ifm->ifa_index = dev->ifindex;
+
+       ci.cstamp = (READ_ONCE(im->mca_cstamp) - INITIAL_JIFFIES) * 100UL / HZ;
+       ci.tstamp = ci.cstamp;
+       ci.ifa_prefered = INFINITY_LIFE_TIME;
+       ci.ifa_valid = INFINITY_LIFE_TIME;
+
+       if (nla_put_in_addr(skb, IFA_MULTICAST, im->multiaddr) < 0 ||
+           nla_put(skb, IFA_CACHEINFO, sizeof(ci), &ci) < 0) {
+               nlmsg_cancel(skb, nlh);
+               return -EMSGSIZE;
+       }
+
+       nlmsg_end(skb, nlh);
+       return 0;
+}
+
+static void inet_ifmcaddr_notify(struct net_device *dev,
+                                const struct ip_mc_list *im, int event)
+{
+       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(__be32)), GFP_ATOMIC);
+       if (!skb)
+               goto error;
+
+       err = inet_fill_ifmcaddr(skb, dev, im, event);
+       if (err < 0) {
+               WARN_ON_ONCE(err == -EMSGSIZE);
+               nlmsg_free(skb);
+               goto error;
+       }
+
+       rtnl_notify(skb, net, 0, RTNLGRP_IPV4_MCADDR, NULL, GFP_ATOMIC);
+       return;
+error:
+       rtnl_set_sk_err(net, RTNLGRP_IPV4_MCADDR, err);
+}
 
 /*
  *     A socket has joined a multicast group on device dev.
@@ -1473,6 +1532,8 @@ static void ____ip_mc_inc_group(struct in_device *in_dev, __be32 addr,
        im->interface = in_dev;
        in_dev_hold(in_dev);
        im->multiaddr = addr;
+       im->mca_cstamp = jiffies;
+       im->mca_tstamp = im->mca_cstamp;
        /* initial mode is (EX, empty) */
        im->sfmode = mode;
        im->sfcount[mode] = 1;
@@ -1492,6 +1553,7 @@ static void ____ip_mc_inc_group(struct in_device *in_dev, __be32 addr,
        igmpv3_del_delrec(in_dev, im);
 #endif
        igmp_group_added(im);
+       inet_ifmcaddr_notify(in_dev->dev, im, RTM_NEWMULTICAST);
        if (!in_dev->dead)
                ip_rt_multicast_event(in_dev);
 out:
@@ -1705,6 +1767,8 @@ void __ip_mc_dec_group(struct in_device *in_dev, __be32 addr, gfp_t gfp)
                                *ip = i->next_rcu;
                                in_dev->mc_count--;
                                __igmp_group_dropped(i, gfp);
+                               inet_ifmcaddr_notify(in_dev->dev, i,
+                                                    RTM_DELMULTICAST);
                                ip_mc_clear_src(i);
 
                                if (!in_dev->dead)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 0e765466d7f79ecc13316204c4ffc29c7ea3a71b..2e2684886953d55140cd3d4a1e024b5218331a49 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5127,22 +5127,6 @@ static inline int inet6_ifaddr_msgsize(void)
               + nla_total_size(4)  /* IFA_RT_PRIORITY */;
 }
 
-enum addr_type_t {
-       UNICAST_ADDR,
-       MULTICAST_ADDR,
-       ANYCAST_ADDR,
-};
-
-struct inet6_fill_args {
-       u32 portid;
-       u32 seq;
-       int event;
-       unsigned int flags;
-       int netnsid;
-       int ifindex;
-       enum addr_type_t type;
-};
-
 static int inet6_fill_ifaddr(struct sk_buff *skb,
                             const struct inet6_ifaddr *ifa,
                             struct inet6_fill_args *args)
@@ -5221,15 +5205,16 @@ error:
        return -EMSGSIZE;
 }
 
-static int inet6_fill_ifmcaddr(struct sk_buff *skb,
-                              const struct ifmcaddr6 *ifmca,
-                              struct inet6_fill_args *args)
+int inet6_fill_ifmcaddr(struct sk_buff *skb,
+                       const struct ifmcaddr6 *ifmca,
+                       struct inet6_fill_args *args)
 {
        int ifindex = ifmca->idev->dev->ifindex;
        u8 scope = RT_SCOPE_UNIVERSE;
        struct nlmsghdr *nlh;
 
-       if (ipv6_addr_scope(&ifmca->mca_addr) & IFA_SITE)
+       if (!args->force_rt_scope_universe &&
+           ipv6_addr_scope(&ifmca->mca_addr) & IFA_SITE)
                scope = RT_SCOPE_SITE;
 
        nlh = nlmsg_put(skb, args->portid, args->seq, args->event,
@@ -5254,6 +5239,7 @@ static int inet6_fill_ifmcaddr(struct sk_buff *skb,
        nlmsg_end(skb, nlh);
        return 0;
 }
+EXPORT_SYMBOL(inet6_fill_ifmcaddr);
 
 static int inet6_fill_ifacaddr(struct sk_buff *skb,
                               const struct ifacaddr6 *ifaca,
@@ -5418,6 +5404,7 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
                .flags = NLM_F_MULTI,
                .netnsid = -1,
                .type = type,
+               .force_rt_scope_universe = false,
        };
        struct {
                unsigned long ifindex;
@@ -5546,6 +5533,7 @@ static int inet6_rtm_getaddr(struct sk_buff *in_skb, struct nlmsghdr *nlh,
                .event = RTM_NEWADDR,
                .flags = 0,
                .netnsid = -1,
+               .force_rt_scope_universe = false,
        };
        struct ifaddrmsg *ifm;
        struct nlattr *tb[IFA_MAX+1];
@@ -5617,6 +5605,7 @@ static void inet6_ifa_notify(int event, struct inet6_ifaddr *ifa)
                .event = event,
                .flags = 0,
                .netnsid = -1,
+               .force_rt_scope_universe = false,
        };
        int err = -ENOBUFS;
 

diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 5ca8692d565d5055eeebef2a547ced217d81c7d4..587831c148deec9524311ca42ebbf9c9de940fb7 100644 (file)
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -33,8 +33,10 @@
 #include <linux/in.h>
 #include <linux/in6.h>
 #include <linux/netdevice.h>
+#include <linux/if_addr.h>
 #include <linux/if_arp.h>
 #include <linux/route.h>
+#include <linux/rtnetlink.h>
 #include <linux/init.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
@@ -47,6 +49,7 @@
 #include <linux/netfilter_ipv6.h>
 
 #include <net/net_namespace.h>
+#include <net/netlink.h>
 #include <net/sock.h>
 #include <net/snmp.h>
 
@@ -901,6 +904,39 @@ static struct ifmcaddr6 *mca_alloc(struct inet6_dev *idev,
        return mc;
 }
 
+static void inet6_ifmcaddr_notify(struct net_device *dev,
+                                 const struct ifmcaddr6 *ifmca, int event)
+{
+       struct inet6_fill_args fillargs = {
+               .portid = 0,
+               .seq = 0,
+               .event = event,
+               .flags = 0,
+               .netnsid = -1,
+               .force_rt_scope_universe = true,
+       };
+       struct net *net = dev_net(dev);
+       struct sk_buff *skb;
+       int err = -ENOMEM;
+
+       skb = nlmsg_new(NLMSG_ALIGN(sizeof(struct ifaddrmsg)) +
+                       nla_total_size(16), GFP_ATOMIC);
+       if (!skb)
+               goto error;
+
+       err = inet6_fill_ifmcaddr(skb, ifmca, &fillargs);
+       if (err < 0) {
+               WARN_ON_ONCE(err == -EMSGSIZE);
+               nlmsg_free(skb);
+               goto error;
+       }
+
+       rtnl_notify(skb, net, 0, RTNLGRP_IPV6_MCADDR, NULL, GFP_ATOMIC);
+       return;
+error:
+       rtnl_set_sk_err(net, RTNLGRP_IPV6_MCADDR, err);
+}
+
 /*
  *     device multicast group inc (add if not found)
  */
@@ -948,6 +984,7 @@ static int __ipv6_dev_mc_inc(struct net_device *dev,
 
        mld_del_delrec(idev, mc);
        igmp6_group_added(mc);
+       inet6_ifmcaddr_notify(dev, mc, RTM_NEWMULTICAST);
        mutex_unlock(&idev->mc_lock);
        ma_put(mc);
        return 0;
@@ -977,6 +1014,8 @@ int __ipv6_dev_mc_dec(struct inet6_dev *idev, const struct in6_addr *addr)
                                *map = ma->next;
 
                                igmp6_group_dropped(ma);
+                               inet6_ifmcaddr_notify(idev->dev, ma,
+                                                     RTM_DELMULTICAST);
                                ip6_mc_clear_src(ma);
                                mutex_unlock(&idev->mc_lock);