Commit 402a8111 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Jakub Kicinski
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ipmr: Convert ipmr_rtm_dumplink() to RCU. 



net->ipv4.mr_tables is updated under RTNL and can be read
safely under RCU.

Once created, the multicast route tables are not removed
until netns dismantle.

ipmr_rtm_dumplink() does not need RTNL protection for
ipmr_for_each_table() and ipmr_fill_table() if RCU is held.

Even if mrt->maxvif changes concurrently, ipmr_fill_vif()
returns true to continue dumping the next table.

Let's convert it to RCU.

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260228221800.1082070-4-kuniyu@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 261950e0

net/ipv4/ipmr.c

+17 −12
Original line number Diff line number Diff line
@@ -2901,12 +2901,13 @@ static bool ipmr_fill_table(struct mr_table *mrt, struct sk_buff *skb) 
	if (nla_put_u32(skb, IPMRA_TABLE_ID, mrt->id) ||

	    nla_put_u32(skb, IPMRA_TABLE_CACHE_RES_QUEUE_LEN, queue_len) ||

	    nla_put_s32(skb, IPMRA_TABLE_MROUTE_REG_VIF_NUM,

			mrt->mroute_reg_vif_num) ||

			READ_ONCE(mrt->mroute_reg_vif_num)) ||

	    nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_ASSERT,

		       mrt->mroute_do_assert) ||

	    nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_PIM, mrt->mroute_do_pim) ||

		       READ_ONCE(mrt->mroute_do_assert)) ||

	    nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_PIM,

		       READ_ONCE(mrt->mroute_do_pim)) ||

	    nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_WRVIFWHOLE,

		       mrt->mroute_do_wrvifwhole))

		       READ_ONCE(mrt->mroute_do_wrvifwhole)))

		return false;



	return true;
@@ -2919,7 +2920,7 @@ static bool ipmr_fill_vif(struct mr_table *mrt, u32 vifid, struct sk_buff *skb) 
	struct vif_device *vif;



	vif = &mrt->vif_table[vifid];

	vif_dev = rtnl_dereference(vif->dev);

	vif_dev = vif_dev_read(vif);

	/* if the VIF doesn't exist just continue */

	if (!vif_dev)

		return true;
@@ -2928,16 +2929,16 @@ static bool ipmr_fill_vif(struct mr_table *mrt, u32 vifid, struct sk_buff *skb) 
	if (!vif_nest)

		return false;



	if (nla_put_u32(skb, IPMRA_VIFA_IFINDEX, vif_dev->ifindex) ||

	if (nla_put_u32(skb, IPMRA_VIFA_IFINDEX, READ_ONCE(vif_dev->ifindex)) ||

	    nla_put_u32(skb, IPMRA_VIFA_VIF_ID, vifid) ||

	    nla_put_u16(skb, IPMRA_VIFA_FLAGS, vif->flags) ||

	    nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_IN, vif->bytes_in,

	    nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_IN, READ_ONCE(vif->bytes_in),

			      IPMRA_VIFA_PAD) ||

	    nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_OUT, vif->bytes_out,

	    nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_OUT, READ_ONCE(vif->bytes_out),

			      IPMRA_VIFA_PAD) ||

	    nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_IN, vif->pkt_in,

	    nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_IN, READ_ONCE(vif->pkt_in),

			      IPMRA_VIFA_PAD) ||

	    nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_OUT, vif->pkt_out,

	    nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_OUT, READ_ONCE(vif->pkt_out),

			      IPMRA_VIFA_PAD) ||

	    nla_put_be32(skb, IPMRA_VIFA_LOCAL_ADDR, vif->local) ||

	    nla_put_be32(skb, IPMRA_VIFA_REMOTE_ADDR, vif->remote)) {
@@ -2992,6 +2993,8 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb) 
	s_t = cb->args[0];

	s_e = cb->args[1];



	rcu_read_lock();



	ipmr_for_each_table(mrt, net) {

		struct nlattr *vifs, *af;

		struct ifinfomsg *hdr;
@@ -3026,7 +3029,7 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb) 
			nlmsg_end(skb, nlh);

			goto out;

		}

		for (i = 0; i < mrt->maxvif; i++) {

		for (i = 0; i < READ_ONCE(mrt->maxvif); i++) {

			if (e < s_e)

				goto skip_entry;

			if (!ipmr_fill_vif(mrt, i, skb)) {
@@ -3048,6 +3051,8 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb) 
	}



out:

	rcu_read_unlock();



	cb->args[1] = e;

	cb->args[0] = t;
@@ -3287,7 +3292,7 @@ static struct pernet_operations ipmr_net_ops = { 


static const struct rtnl_msg_handler ipmr_rtnl_msg_handlers[] __initconst = {

	{.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_GETLINK,

	 .dumpit = ipmr_rtm_dumplink},

	 .dumpit = ipmr_rtm_dumplink, .flags = RTNL_FLAG_DUMP_UNLOCKED},

	{.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_NEWROUTE,

	 .doit = ipmr_rtm_route},

	{.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_DELROUTE,