Commit bd085ef6 authored by Hangbin Liu's avatar Hangbin Liu Committed by David S. Miller
Browse files

net: add bool confirm_neigh parameter for dst_ops.update_pmtu 



The MTU update code is supposed to be invoked in response to real
networking events that update the PMTU. In IPv6 PMTU update function
__ip6_rt_update_pmtu() we called dst_confirm_neigh() to update neighbor
confirmed time.

But for tunnel code, it will call pmtu before xmit, like:
  - tnl_update_pmtu()
    - skb_dst_update_pmtu()
      - ip6_rt_update_pmtu()
        - __ip6_rt_update_pmtu()
          - dst_confirm_neigh()

If the tunnel remote dst mac address changed and we still do the neigh
confirm, we will not be able to update neigh cache and ping6 remote
will failed.

So for this ip_tunnel_xmit() case, _EVEN_ if the MTU is changed, we
should not be invoking dst_confirm_neigh() as we have no evidence
of successful two-way communication at this point.

On the other hand it is also important to keep the neigh reachability fresh
for TCP flows, so we cannot remove this dst_confirm_neigh() call.

To fix the issue, we have to add a new bool parameter for dst_ops.update_pmtu
to choose whether we should do neigh update or not. I will add the parameter
in this patch and set all the callers to true to comply with the previous
way, and fix the tunnel code one by one on later patches.

v5: No change.
v4: No change.
v3: Do not remove dst_confirm_neigh, but add a new bool parameter in
    dst_ops.update_pmtu to control whether we should do neighbor confirm.
    Also split the big patch to small ones for each area.
v2: Remove dst_confirm_neigh in __ip6_rt_update_pmtu.

Suggested-by: default avatarDavid Miller <davem@davemloft.net>
Reviewed-by: default avatarGuillaume Nault <gnault@redhat.com>
Acked-by: default avatarDavid Ahern <dsahern@gmail.com>
Signed-off-by: default avatarHangbin Liu <liuhangbin@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ff43ae4b

drivers/net/gtp.c

+1 −1
Original line number Diff line number Diff line
@@ -540,7 +540,7 @@ static int gtp_build_skb_ip4(struct sk_buff *skb, struct net_device *dev, 
		mtu = dst_mtu(&rt->dst);

	}



	rt->dst.ops->update_pmtu(&rt->dst, NULL, skb, mtu);

	rt->dst.ops->update_pmtu(&rt->dst, NULL, skb, mtu, true);



	if (!skb_is_gso(skb) && (iph->frag_off & htons(IP_DF)) &&

	    mtu < ntohs(iph->tot_len)) {

include/net/dst.h

+1 −1
Original line number Diff line number Diff line
@@ -516,7 +516,7 @@ static inline void skb_dst_update_pmtu(struct sk_buff *skb, u32 mtu) 
	struct dst_entry *dst = skb_dst(skb);



	if (dst && dst->ops->update_pmtu)

		dst->ops->update_pmtu(dst, NULL, skb, mtu);

		dst->ops->update_pmtu(dst, NULL, skb, mtu, true);

}



static inline void skb_tunnel_check_pmtu(struct sk_buff *skb,

include/net/dst_ops.h

+2 −1
Original line number Diff line number Diff line
@@ -27,7 +27,8 @@ struct dst_ops { 
	struct dst_entry *	(*negative_advice)(struct dst_entry *);

	void			(*link_failure)(struct sk_buff *);

	void			(*update_pmtu)(struct dst_entry *dst, struct sock *sk,

					       struct sk_buff *skb, u32 mtu);

					       struct sk_buff *skb, u32 mtu,

					       bool confirm_neigh);

	void			(*redirect)(struct dst_entry *dst, struct sock *sk,

					    struct sk_buff *skb);

	int			(*local_out)(struct net *net, struct sock *sk, struct sk_buff *skb);

net/bridge/br_nf_core.c

+2 −1
Original line number Diff line number Diff line
@@ -22,7 +22,8 @@ 
#endif



static void fake_update_pmtu(struct dst_entry *dst, struct sock *sk,

			     struct sk_buff *skb, u32 mtu)

			     struct sk_buff *skb, u32 mtu,

			     bool confirm_neigh)

{

}

net/decnet/dn_route.c

+4 −2
Original line number Diff line number Diff line
@@ -110,7 +110,8 @@ static void dn_dst_ifdown(struct dst_entry *, struct net_device *dev, int how); 
static struct dst_entry *dn_dst_negative_advice(struct dst_entry *);

static void dn_dst_link_failure(struct sk_buff *);

static void dn_dst_update_pmtu(struct dst_entry *dst, struct sock *sk,

			       struct sk_buff *skb , u32 mtu);

			       struct sk_buff *skb , u32 mtu,

			       bool confirm_neigh);

static void dn_dst_redirect(struct dst_entry *dst, struct sock *sk,

			    struct sk_buff *skb);

static struct neighbour *dn_dst_neigh_lookup(const struct dst_entry *dst,
@@ -251,7 +252,8 @@ static int dn_dst_gc(struct dst_ops *ops) 
 * advertise to the other end).

 */

static void dn_dst_update_pmtu(struct dst_entry *dst, struct sock *sk,

			       struct sk_buff *skb, u32 mtu)

			       struct sk_buff *skb, u32 mtu,

			       bool confirm_neigh)

{

	struct dn_route *rt = (struct dn_route *) dst;

	struct neighbour *n = rt->n;

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