Re: [PATCH net-next] netlink: add igmp join/leave notifications

[Hangbin Liu <liuhangbin@gmail.com>]

Hi Yuyang,

Would you mind also update iproute2 for testing?
On Sun, Nov 10, 2024 at 05:19:53PM +0900, Yuyang Huang wrote:
> This change introduces netlink notifications for multicast address
> changes, enabling components like the Android Packet Filter to implement
> IGMP offload solutions.
> 
> The following features are included:
> * Addition and deletion of multicast addresses are reported using
>   RTM_NEWMULTICAST and RTM_DELMULTICAST messages with AF_INET.
> * A new notification group, RTNLGRP_IPV4_MCADDR, is introduced for
>   receiving these events.
> 
> This enhancement allows user-space components to efficiently track
> multicast group memberships and program hardware offload filters
> accordingly.
> 
> 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>
> ---
>  include/uapi/linux/rtnetlink.h |  6 ++++
>  net/ipv4/igmp.c                | 58 ++++++++++++++++++++++++++++++++++
>  2 files changed, 64 insertions(+)
> 
> diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
> index 3b687d20c9ed..354a923f129d 100644
> --- a/include/uapi/linux/rtnetlink.h
> +++ b/include/uapi/linux/rtnetlink.h
> @@ -93,6 +93,10 @@ enum {
>  	RTM_NEWPREFIX	= 52,
>  #define RTM_NEWPREFIX	RTM_NEWPREFIX
>  
> +	RTM_NEWMULTICAST,
> +#define RTM_NEWMULTICAST RTM_NEWMULTICAST
> +	RTM_DELMULTICAST,
> +#define RTM_DELMULTICAST RTM_DELMULTICAST
>  	RTM_GETMULTICAST = 58,
>  #define RTM_GETMULTICAST RTM_GETMULTICAST
>  
> @@ -774,6 +778,8 @@ 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_MAX
>  };
>  #define RTNLGRP_MAX	(__RTNLGRP_MAX - 1)
> diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
> index 9bf09de6a2e7..34575f5392a8 100644
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -88,6 +88,7 @@
>  #include <linux/byteorder/generic.h>
>  
>  #include <net/net_namespace.h>
> +#include <net/netlink.h>
>  #include <net/arp.h>
>  #include <net/ip.h>
>  #include <net/protocol.h>
> @@ -1430,6 +1431,60 @@ 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,
> +			      __be32 addr, int event)
> +{
> +	struct nlmsghdr *nlh;
> +	struct ifaddrmsg *ifm;
> +
> +	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_LINK;
> +	ifm->ifa_index = dev->ifindex;
> +
> +	if (nla_put_in_addr(skb, IFA_MULTICAST, addr) < 0) {
> +		nlmsg_cancel(skb, nlh);
> +		return -EMSGSIZE;
> +	}
> +
> +	nlmsg_end(skb, nlh);
> +	return 0;
> +}
> +
> +static inline int inet_ifmcaddr_msgsize(void)
> +{
> +	return NLMSG_ALIGN(sizeof(struct ifaddrmsg))
> +			+ nla_total_size(sizeof(__be32));
> +}
> +
> +static void inet_ifmcaddr_notify(struct net_device *dev, __be32 addr, int event)
> +{
> +	struct net *net = dev_net(dev);
> +	struct sk_buff *skb;
> +	int err = -ENOBUFS;
> +
> +	skb = nlmsg_new(inet_ifmcaddr_msgsize(), GFP_ATOMIC);
> +	if (!skb)
> +		goto error;
> +
> +	err = inet_fill_ifmcaddr(skb, dev, addr, event);
> +	if (err < 0) {
> +		WARN_ON(err == -EMSGSIZE);
> +		kfree_skb(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.
> @@ -1476,6 +1531,7 @@ 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, addr, RTM_NEWMULTICAST);
>  	if (!in_dev->dead)
>  		ip_rt_multicast_event(in_dev);
>  out:
> @@ -1689,6 +1745,8 @@ 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, addr,
> +						     RTM_DELMULTICAST);
>  				ip_mc_clear_src(i);
>  
>  				if (!in_dev->dead)
> -- 
> 2.47.0.277.g8800431eea-goog
>