[PATCH net-next] mctp: emit RTM_NEWADDR and RTM_DELADDR

[PATCH net-next] mctp: emit RTM_NEWADDR and RTM_DELADDR

[Matt Johnston]

Userspace can receive notification of MCTP address changes via
RTNLGRP_MCTP_IFADDR rtnetlink multicast group.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
---
 include/uapi/linux/rtnetlink.h |  2 ++
 net/mctp/device.c              | 55 ++++++++++++++++++++++++++++++----
 2 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index 5888492a5257..93d934cc4613 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -754,6 +754,8 @@ enum rtnetlink_groups {
 #define RTNLGRP_NEXTHOP		RTNLGRP_NEXTHOP
 	RTNLGRP_BRVLAN,
 #define RTNLGRP_BRVLAN		RTNLGRP_BRVLAN
+	RTNLGRP_MCTP_IFADDR,
+#define RTNLGRP_MCTP_IFADDR	RTNLGRP_MCTP_IFADDR
 	__RTNLGRP_MAX
 };
 #define RTNLGRP_MAX	(__RTNLGRP_MAX - 1)
diff --git a/net/mctp/device.c b/net/mctp/device.c
index 8799ee77e7b7..6db71127c4cb 100644
--- a/net/mctp/device.c
+++ b/net/mctp/device.c
@@ -35,14 +35,24 @@ struct mctp_dev *mctp_dev_get_rtnl(const struct net_device *dev)
 	return rtnl_dereference(dev->mctp_ptr);
 }
 
-static int mctp_fill_addrinfo(struct sk_buff *skb, struct netlink_callback *cb,
-			      struct mctp_dev *mdev, mctp_eid_t eid)
+static int mctp_addrinfo_size(void)
+{
+	return NLMSG_ALIGN(sizeof(struct ifaddrmsg))
+		+ nla_total_size(4) // IFA_LOCAL
+		+ nla_total_size(4) // IFA_ADDRESS
+		;
+}
+
+/* flag should be NLM_F_MULTI for dump calls */
+static int mctp_fill_addrinfo(struct sk_buff *skb,
+			      struct mctp_dev *mdev, mctp_eid_t eid,
+			      int msg_type, u32 portid, u32 seq, int flag)
 {
 	struct ifaddrmsg *hdr;
 	struct nlmsghdr *nlh;
 
-	nlh = nlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
-			RTM_NEWADDR, sizeof(*hdr), NLM_F_MULTI);
+	nlh = nlmsg_put(skb, portid, seq,
+			msg_type, sizeof(*hdr), flag);
 	if (!nlh)
 		return -EMSGSIZE;
 
@@ -73,9 +83,13 @@ static int mctp_dump_dev_addrinfo(struct mctp_dev *mdev, struct sk_buff *skb,
 {
 	struct mctp_dump_cb *mcb = (void *)cb->ctx;
 	int rc = 0;
+	u32 portid, seq;
 
+	portid = NETLINK_CB(cb->skb).portid;
+	seq = cb->nlh->nlmsg_seq;
 	for (; mcb->a_idx < mdev->num_addrs; mcb->a_idx++) {
-		rc = mctp_fill_addrinfo(skb, cb, mdev, mdev->addrs[mcb->a_idx]);
+		rc = mctp_fill_addrinfo(skb, mdev, mdev->addrs[mcb->a_idx],
+					RTM_NEWADDR, portid, seq, NLM_F_MULTI);
 		if (rc < 0)
 			break;
 	}
@@ -127,6 +141,34 @@ static int mctp_dump_addrinfo(struct sk_buff *skb, struct netlink_callback *cb)
 	return skb->len;
 }
 
+static void mctp_addr_notify(struct mctp_dev *mdev, mctp_eid_t eid, int msg_type,
+			     struct sk_buff *req_skb, struct nlmsghdr *req_nlh)
+{
+	int rc;
+	struct sk_buff *skb;
+	struct net *net = dev_net(mdev->dev);
+	u32 portid = NETLINK_CB(req_skb).portid;
+
+	skb = nlmsg_new(mctp_addrinfo_size(), GFP_KERNEL);
+	if (!skb) {
+		rc = -ENOBUFS;
+		goto out;
+	}
+
+	rc = mctp_fill_addrinfo(skb, mdev, eid, msg_type,
+				portid, req_nlh->nlmsg_seq, 0);
+	if (rc < 0)
+		goto out;
+
+	rtnl_notify(skb, net, portid, RTNLGRP_MCTP_IFADDR, req_nlh, GFP_KERNEL);
+out:
+	if (rc < 0) {
+		if (skb)
+			kfree_skb(skb);
+		rtnl_set_sk_err(net, RTNLGRP_MCTP_IFADDR, rc);
+	}
+}
+
 static const struct nla_policy ifa_mctp_policy[IFA_MAX + 1] = {
 	[IFA_ADDRESS]		= { .type = NLA_U8 },
 	[IFA_LOCAL]		= { .type = NLA_U8 },
@@ -189,6 +231,7 @@ static int mctp_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 	kfree(tmp_addrs);
 
+	mctp_addr_notify(mdev, addr->s_addr, RTM_NEWADDR, skb, nlh);
 	mctp_route_add_local(mdev, addr->s_addr);
 
 	return 0;
@@ -244,6 +287,8 @@ static int mctp_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh,
 	mdev->num_addrs--;
 	spin_unlock_irqrestore(&mdev->addrs_lock, flags);
 
+	mctp_addr_notify(mdev, addr->s_addr, RTM_DELADDR, skb, nlh);
+
 	return 0;
 }
 
-- 
2.32.0

Re: [PATCH net-next] mctp: emit RTM_NEWADDR and RTM_DELADDR

[Jeremy Kerr]

Hi Matt,

> Userspace can receive notification of MCTP address changes via
> RTNLGRP_MCTP_IFADDR rtnetlink multicast group.

Nice! A couple of minor things:

> +static void mctp_addr_notify(struct mctp_dev *mdev, mctp_eid_t eid, int msg_type,
> +                            struct sk_buff *req_skb, struct nlmsghdr *req_nlh)

Is it worthwhile keeping the portid argument here, rather than the
entire request skb? Might prevent some confusion with the notify skb.

(I'm OK if we settle on the req_skb approach too though, as it does save
a little repeated code in call sites)

> +{
> +       int rc;
> +       struct sk_buff *skb;
> +       struct net *net = dev_net(mdev->dev);
> +       u32 portid = NETLINK_CB(req_skb).portid;

Super minor, but: reverse Christmas tree here (and above)?

> +
> +       skb = nlmsg_new(mctp_addrinfo_size(), GFP_KERNEL);
> +       if (!skb) {
> +               rc = -ENOBUFS;
> +               goto out;
> +       }
> +
> +       rc = mctp_fill_addrinfo(skb, mdev, eid, msg_type,
> +                               portid, req_nlh->nlmsg_seq, 0);
> +       if (rc < 0)
> +               goto out;
> +
> +       rtnl_notify(skb, net, portid, RTNLGRP_MCTP_IFADDR, req_nlh,
> GFP_KERNEL);
> +out:
> +       if (rc < 0) {
> +               if (skb)
> +                       kfree_skb(skb);
> +               rtnl_set_sk_err(net, RTNLGRP_MCTP_IFADDR, rc);
> +       }

We don't need that `if (skb)` condition on the kfree_skb - Yang has
removed a bunch in 5cfe53cfeb1. We could also remove the rc check if we
use the goto-label only for errors. Maybe something like:

            rtnl_notify(skb, net, portid, RTNLGRP_MCTP_IFADDR, req_nlh, GFP_KERNEL);
            return;
    err:
            kfree_skb(skb);
            rtnl_set_sk_err(net, RTNLGRP_MCTP_IFADDR, rc);
    }

Cheers,


Jeremy