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bd085ef678
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: David Miller <davem@davemloft.net>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Acked-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
91 lines
2 KiB
C
91 lines
2 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Handle firewalling core
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* Linux ethernet bridge
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*
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* Authors:
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* Lennert Buytenhek <buytenh@gnu.org>
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* Bart De Schuymer <bdschuym@pandora.be>
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*
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* Lennert dedicates this file to Kerstin Wurdinger.
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/in_route.h>
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#include <linux/inetdevice.h>
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#include <net/route.h>
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#include "br_private.h"
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#ifdef CONFIG_SYSCTL
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#include <linux/sysctl.h>
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#endif
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static void fake_update_pmtu(struct dst_entry *dst, struct sock *sk,
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struct sk_buff *skb, u32 mtu,
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bool confirm_neigh)
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{
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}
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static void fake_redirect(struct dst_entry *dst, struct sock *sk,
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struct sk_buff *skb)
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{
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}
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static u32 *fake_cow_metrics(struct dst_entry *dst, unsigned long old)
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{
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return NULL;
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}
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static struct neighbour *fake_neigh_lookup(const struct dst_entry *dst,
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struct sk_buff *skb,
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const void *daddr)
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{
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return NULL;
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}
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static unsigned int fake_mtu(const struct dst_entry *dst)
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{
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return dst->dev->mtu;
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}
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static struct dst_ops fake_dst_ops = {
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.family = AF_INET,
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.update_pmtu = fake_update_pmtu,
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.redirect = fake_redirect,
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.cow_metrics = fake_cow_metrics,
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.neigh_lookup = fake_neigh_lookup,
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.mtu = fake_mtu,
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};
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/*
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* Initialize bogus route table used to keep netfilter happy.
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* Currently, we fill in the PMTU entry because netfilter
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* refragmentation needs it, and the rt_flags entry because
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* ipt_REJECT needs it. Future netfilter modules might
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* require us to fill additional fields.
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*/
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static const u32 br_dst_default_metrics[RTAX_MAX] = {
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[RTAX_MTU - 1] = 1500,
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};
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void br_netfilter_rtable_init(struct net_bridge *br)
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{
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struct rtable *rt = &br->fake_rtable;
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atomic_set(&rt->dst.__refcnt, 1);
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rt->dst.dev = br->dev;
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dst_init_metrics(&rt->dst, br_dst_default_metrics, true);
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rt->dst.flags = DST_NOXFRM | DST_FAKE_RTABLE;
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rt->dst.ops = &fake_dst_ops;
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}
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int __init br_nf_core_init(void)
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{
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return dst_entries_init(&fake_dst_ops);
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}
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void br_nf_core_fini(void)
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{
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dst_entries_destroy(&fake_dst_ops);
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}
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