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Message-ID: <6cb2b3e2-d3ce-427e-9809-5b81474b80e4@6wind.com>
Date: Wed, 4 Dec 2024 14:53:59 +0100
From: Nicolas Dichtel <nicolas.dichtel@...nd.com>
To: Yuyang Huang <yuyanghuang@...gle.com>
Cc: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
David Ahern <dsahern@...nel.org>, roopa@...ulusnetworks.com,
jiri@...nulli.us, stephen@...workplumber.org, jimictw@...gle.com,
prohr@...gle.com, liuhangbin@...il.com, andrew@...n.ch,
netdev@...r.kernel.org, Maciej Żenczykowski
<maze@...gle.com>, Lorenzo Colitti <lorenzo@...gle.com>,
Patrick Ruddy <pruddy@...tta.att-mail.com>
Subject: Re: [PATCH net-next, v4] netlink: add IGMP/MLD join/leave
notifications
Le 04/12/2024 à 14:47, Yuyang Huang a écrit :
> 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@...gle.com>
> Cc: Lorenzo Colitti <lorenzo@...gle.com>
> Co-developed-by: Patrick Ruddy <pruddy@...tta.att-mail.com>
> Signed-off-by: Patrick Ruddy <pruddy@...tta.att-mail.com>
> Link: https://lore.kernel.org/r/20180906091056.21109-1-pruddy@vyatta.att-mail.com
> Signed-off-by: Yuyang Huang <yuyanghuang@...gle.com>
A minor comment below and then:
Acked-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
> ---
>
> Changelog since v3:
> - Remove unused variable 'scope' declaration.
> - Align RTM_NEWMULTICAST and RTM_GETMULTICAST enum definitions with
> existing code style.
>
> Changelog since v2:
> - Use RT_SCOPE_UNIVERSE for both IGMP and MLD notification messages for
> consistency.
>
> Changelog since v1:
> - Implement MLD join/leave notifications.
> - Revise the comment message to make it generic.
> - Fix netdev/source_inline error.
> - Reorder local variables according to "reverse xmas tree” style.
>
> include/uapi/linux/rtnetlink.h | 10 +++++-
> net/ipv4/igmp.c | 53 +++++++++++++++++++++++++++++++
> net/ipv6/mcast.c | 57 ++++++++++++++++++++++++++++++++++
> 3 files changed, 119 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
> index db7254d52d93..eccc0e7dcb7d 100644
> --- 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 6a238398acc9..8d6ee19864c6 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 +1431,55 @@ 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 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;
> +
> + if (nla_put_in_addr(skb, IFA_MULTICAST, addr) < 0) {
> + nlmsg_cancel(skb, nlh);
> + return -EMSGSIZE;
> + }
> +
> + nlmsg_end(skb, nlh);
> + return 0;
> +}
> +
> +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(NLMSG_ALIGN(sizeof(struct ifaddrmsg))
> + + nla_total_size(sizeof(__be32)), GFP_ATOMIC);
> + if (!skb)
> + goto error;
> +
> + err = inet_fill_ifmcaddr(skb, dev, addr, event);
> + if (err < 0) {
> + WARN_ON(err == -EMSGSIZE);
Maybe WARN_ON_ONCE() is enough?
Regards,
Nicolas
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