Commit 6b724bc4 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

ipv6: lockless IPV6_MTU_DISCOVER implementation 



Most np->pmtudisc reads are racy.

Move this 3bit field on a full byte, add annotations
and make IPV6_MTU_DISCOVER setsockopt() lockless.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarDavid Ahern <dsahern@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 83cd5eb6

include/linux/ipv6.h

+2 −3
Original line number Diff line number Diff line
@@ -243,13 +243,12 @@ struct ipv6_pinfo { 
	} rxopt;



	/* sockopt flags */

	__u16			sndflow:1,

				pmtudisc:3,

				padding:1,	/* 1 bit hole */

	__u8			sndflow:1,

				srcprefs:3;	/* 001: prefer temporary address

						 * 010: prefer public address

						 * 100: prefer care-of address

						 */

	__u8			pmtudisc;

	__u8			min_hopcount;

	__u8			tclass;

	__be32			rcv_flowinfo;

include/net/ip6_route.h

+9 −5
Original line number Diff line number Diff line
@@ -266,7 +266,7 @@ static inline unsigned int ip6_skb_dst_mtu(const struct sk_buff *skb) 
	const struct dst_entry *dst = skb_dst(skb);

	unsigned int mtu;



	if (np && np->pmtudisc >= IPV6_PMTUDISC_PROBE) {

	if (np && READ_ONCE(np->pmtudisc) >= IPV6_PMTUDISC_PROBE) {

		mtu = READ_ONCE(dst->dev->mtu);

		mtu -= lwtunnel_headroom(dst->lwtstate, mtu);

	} else {
@@ -277,14 +277,18 @@ static inline unsigned int ip6_skb_dst_mtu(const struct sk_buff *skb) 


static inline bool ip6_sk_accept_pmtu(const struct sock *sk)

{

	return inet6_sk(sk)->pmtudisc != IPV6_PMTUDISC_INTERFACE &&

	       inet6_sk(sk)->pmtudisc != IPV6_PMTUDISC_OMIT;

	u8 pmtudisc = READ_ONCE(inet6_sk(sk)->pmtudisc);



	return pmtudisc != IPV6_PMTUDISC_INTERFACE &&

	       pmtudisc != IPV6_PMTUDISC_OMIT;

}



static inline bool ip6_sk_ignore_df(const struct sock *sk)

{

	return inet6_sk(sk)->pmtudisc < IPV6_PMTUDISC_DO ||

	       inet6_sk(sk)->pmtudisc == IPV6_PMTUDISC_OMIT;

	u8 pmtudisc = READ_ONCE(inet6_sk(sk)->pmtudisc);



	return pmtudisc < IPV6_PMTUDISC_DO ||

	       pmtudisc == IPV6_PMTUDISC_OMIT;

}



static inline const struct in6_addr *rt6_nexthop(const struct rt6_info *rt,

net/ipv6/ip6_output.c

+2 −2
Original line number Diff line number Diff line
@@ -1436,10 +1436,10 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork, 
	v6_cork->hop_limit = ipc6->hlimit;

	v6_cork->tclass = ipc6->tclass;

	if (rt->dst.flags & DST_XFRM_TUNNEL)

		mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ?

		mtu = READ_ONCE(np->pmtudisc) >= IPV6_PMTUDISC_PROBE ?

		      READ_ONCE(rt->dst.dev->mtu) : dst_mtu(&rt->dst);

	else

		mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ?

		mtu = READ_ONCE(np->pmtudisc) >= IPV6_PMTUDISC_PROBE ?

			READ_ONCE(rt->dst.dev->mtu) : dst_mtu(xfrm_dst_path(&rt->dst));



	frag_size = READ_ONCE(np->frag_size);

net/ipv6/ipv6_sockglue.c

+8 −9
Original line number Diff line number Diff line
@@ -493,6 +493,13 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname, 
			return -EINVAL;

		inet6_assign_bit(RTALERT_ISOLATE, sk, valbool);

		return 0;

	case IPV6_MTU_DISCOVER:

		if (optlen < sizeof(int))

			return -EINVAL;

		if (val < IPV6_PMTUDISC_DONT || val > IPV6_PMTUDISC_OMIT)

			return -EINVAL;

		WRITE_ONCE(np->pmtudisc, val);

		return 0;

	}

	if (needs_rtnl)

		rtnl_lock();
@@ -941,14 +948,6 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname, 
			goto e_inval;

		retv = ip6_ra_control(sk, val);

		break;

	case IPV6_MTU_DISCOVER:

		if (optlen < sizeof(int))

			goto e_inval;

		if (val < IPV6_PMTUDISC_DONT || val > IPV6_PMTUDISC_OMIT)

			goto e_inval;

		np->pmtudisc = val;

		retv = 0;

		break;

	case IPV6_FLOWINFO_SEND:

		if (optlen < sizeof(int))

			goto e_inval;
@@ -1374,7 +1373,7 @@ int do_ipv6_getsockopt(struct sock *sk, int level, int optname, 
		break;



	case IPV6_MTU_DISCOVER:

		val = np->pmtudisc;

		val = READ_ONCE(np->pmtudisc);

		break;



	case IPV6_RECVERR:

net/ipv6/raw.c

+1 −1
Original line number Diff line number Diff line
@@ -307,7 +307,7 @@ static void rawv6_err(struct sock *sk, struct sk_buff *skb, 
	harderr = icmpv6_err_convert(type, code, &err);

	if (type == ICMPV6_PKT_TOOBIG) {

		ip6_sk_update_pmtu(skb, sk, info);

		harderr = (np->pmtudisc == IPV6_PMTUDISC_DO);

		harderr = (READ_ONCE(np->pmtudisc) == IPV6_PMTUDISC_DO);

	}

	if (type == NDISC_REDIRECT) {

		ip6_sk_redirect(skb, sk);