Commit e804bd83 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Jakub Kicinski
Browse files

neighbour: Split pneigh_lookup(). 



pneigh_lookup() has ASSERT_RTNL() in the middle of the function, which
is confusing.

When called with the last argument, creat, 0, pneigh_lookup() literally
looks up a proxy neighbour entry.  This is the case of the reader path
as the fast path and RTM_GETNEIGH.

pneigh_lookup(), however, creates a pneigh_entry when called with creat 1
from RTM_NEWNEIGH and SIOCSARP, which require RTNL.

Let's split pneigh_lookup() into two functions.

We will convert all the reader paths to RCU, and read_lock_bh(&tbl->lock)
in the new pneigh_lookup() will be dropped.

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-6-kuniyu@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 0e5ac19c

include/net/neighbour.h

+3 −2
Original line number Diff line number Diff line
@@ -376,10 +376,11 @@ unsigned long neigh_rand_reach_time(unsigned long base); 
void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p,

		    struct sk_buff *skb);

struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl, struct net *net,

				   const void *key, struct net_device *dev,

				   int creat);

				   const void *key, struct net_device *dev);

struct pneigh_entry *__pneigh_lookup(struct neigh_table *tbl, struct net *net,

				     const void *key, struct net_device *dev);

struct pneigh_entry *pneigh_create(struct neigh_table *tbl, struct net *net,

				   const void *key, struct net_device *dev);

int pneigh_delete(struct neigh_table *tbl, struct net *net, const void *key,

		  struct net_device *dev);

net/core/neighbour.c

+29 −10
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <net/neighbour.h>

#include <net/arp.h>

#include <net/dst.h>

#include <net/ip.h>

#include <net/sock.h>

#include <net/netevent.h>

#include <net/netlink.h>
@@ -748,22 +749,42 @@ EXPORT_SYMBOL_GPL(__pneigh_lookup); 


struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl,

				   struct net *net, const void *pkey,

				    struct net_device *dev, int creat)

				   struct net_device *dev)

{

	struct pneigh_entry *n;

	unsigned int key_len;

	u32 hash_val;



	key_len = tbl->key_len;

	hash_val = pneigh_hash(pkey, key_len);



	read_lock_bh(&tbl->lock);

	n = __pneigh_lookup_1(tbl->phash_buckets[hash_val],

			      net, pkey, key_len, dev);

	read_unlock_bh(&tbl->lock);



	return n;

}

EXPORT_IPV6_MOD(pneigh_lookup);



struct pneigh_entry *pneigh_create(struct neigh_table *tbl,

				   struct net *net, const void *pkey,

				   struct net_device *dev)

{

	struct pneigh_entry *n;

	unsigned int key_len = tbl->key_len;

	u32 hash_val = pneigh_hash(pkey, key_len);



	ASSERT_RTNL();



	read_lock_bh(&tbl->lock);

	n = __pneigh_lookup_1(tbl->phash_buckets[hash_val],

			      net, pkey, key_len, dev);

	read_unlock_bh(&tbl->lock);



	if (n || !creat)

	if (n)

		goto out;



	ASSERT_RTNL();



	n = kzalloc(sizeof(*n) + key_len, GFP_KERNEL);

	if (!n)

		goto out;
@@ -787,8 +808,6 @@ struct pneigh_entry * pneigh_lookup(struct neigh_table *tbl, 
out:

	return n;

}

EXPORT_SYMBOL(pneigh_lookup);





int pneigh_delete(struct neigh_table *tbl, struct net *net, const void *pkey,

		  struct net_device *dev)
@@ -2007,7 +2026,7 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh, 
		}



		err = -ENOBUFS;

		pn = pneigh_lookup(tbl, net, dst, dev, 1);

		pn = pneigh_create(tbl, net, dst, dev);

		if (pn) {

			pn->flags = ndm_flags;

			pn->permanent = !!(ndm->ndm_state & NUD_PERMANENT);
@@ -3036,7 +3055,7 @@ static int neigh_get(struct sk_buff *in_skb, struct nlmsghdr *nlh, 
	if (ndm->ndm_flags & NTF_PROXY) {

		struct pneigh_entry *pn;



		pn = pneigh_lookup(tbl, net, dst, dev, 0);

		pn = pneigh_lookup(tbl, net, dst, dev);

		if (!pn) {

			NL_SET_ERR_MSG(extack, "Proxy neighbour entry not found");

			err = -ENOENT;

net/ipv4/arp.c

+2 −2
Original line number Diff line number Diff line
@@ -864,7 +864,7 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb) 
			    (arp_fwd_proxy(in_dev, dev, rt) ||

			     arp_fwd_pvlan(in_dev, dev, rt, sip, tip) ||

			     (rt->dst.dev != dev &&

			      pneigh_lookup(&arp_tbl, net, &tip, dev, 0)))) {

			      pneigh_lookup(&arp_tbl, net, &tip, dev)))) {

				n = neigh_event_ns(&arp_tbl, sha, &sip, dev);

				if (n)

					neigh_release(n);
@@ -1089,7 +1089,7 @@ static int arp_req_set_public(struct net *net, struct arpreq *r, 
	if (mask) {

		__be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;



		if (!pneigh_lookup(&arp_tbl, net, &ip, dev, 1))

		if (!pneigh_create(&arp_tbl, net, &ip, dev))

			return -ENOBUFS;

		return 0;

	}

net/ipv6/ip6_output.c

+1 −1
Original line number Diff line number Diff line
@@ -563,7 +563,7 @@ int ip6_forward(struct sk_buff *skb) 


	/* XXX: idev->cnf.proxy_ndp? */

	if (READ_ONCE(net->ipv6.devconf_all->proxy_ndp) &&

	    pneigh_lookup(&nd_tbl, net, &hdr->daddr, skb->dev, 0)) {

	    pneigh_lookup(&nd_tbl, net, &hdr->daddr, skb->dev)) {

		int proxied = ip6_forward_proxy_check(skb);

		if (proxied > 0) {

			/* It's tempting to decrease the hop limit

net/ipv6/ndisc.c

+1 −1
Original line number Diff line number Diff line
@@ -1100,7 +1100,7 @@ static enum skb_drop_reason ndisc_recv_na(struct sk_buff *skb) 
		if (lladdr && !memcmp(lladdr, dev->dev_addr, dev->addr_len) &&

		    READ_ONCE(net->ipv6.devconf_all->forwarding) &&

		    READ_ONCE(net->ipv6.devconf_all->proxy_ndp) &&

		    pneigh_lookup(&nd_tbl, net, &msg->target, dev, 0)) {

		    pneigh_lookup(&nd_tbl, net, &msg->target, dev)) {

			/* XXX: idev->cnf.proxy_ndp */

			goto out;

		}