* [PATCH] tap: Don't update ip6.addr_seen to ::
@ 2023-05-16 0:36 David Gibson
2023-05-17 19:40 ` Stefano Brivio
0 siblings, 1 reply; 2+ messages in thread
From: David Gibson @ 2023-05-16 0:36 UTC (permalink / raw)
To: passt-dev, Stefano Brivio; +Cc: David Gibson
When we receive packets from the tap side, we update the addr_seen fields
to reflect the last known address of the guest or ns. For ip4.addr_seen
we, sensibly, only update if the address we've just seen isn't 0 (0.0.0.0).
This case can occur during early DHCP transactions.
We have no equivalent case for IPv6. We're less likely to hit this,
because DHCPv6 uses link-local addresses, however we can see an source
address of :: with certain multicast operations. This can bite us if we
try to make an incoming connection very early after starting pasta with
--config-net: we may have only seen some of those multicast packets,
updated addr_seen to :: and not had any "real" packets to update it to a
global address. I've seen this with some of the avocado test conversions.
In any case, it can never make sense to update addr_seen to ::, so
explicitly exclude that case.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
tap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tap.c b/tap.c
index faa4e26..c0b7f33 100644
--- a/tap.c
+++ b/tap.c
@@ -739,7 +739,7 @@ resume:
if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_seen)) {
c->ip6.addr_seen = *saddr;
}
- } else {
+ } else if (!IN6_IS_ADDR_UNSPECIFIED(saddr)){
c->ip6.addr_seen = *saddr;
}
--
@@ -739,7 +739,7 @@ resume:
if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_seen)) {
c->ip6.addr_seen = *saddr;
}
- } else {
+ } else if (!IN6_IS_ADDR_UNSPECIFIED(saddr)){
c->ip6.addr_seen = *saddr;
}
--
2.40.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] tap: Don't update ip6.addr_seen to ::
2023-05-16 0:36 [PATCH] tap: Don't update ip6.addr_seen to :: David Gibson
@ 2023-05-17 19:40 ` Stefano Brivio
0 siblings, 0 replies; 2+ messages in thread
From: Stefano Brivio @ 2023-05-17 19:40 UTC (permalink / raw)
To: David Gibson; +Cc: passt-dev
On Tue, 16 May 2023 10:36:11 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:
> When we receive packets from the tap side, we update the addr_seen fields
> to reflect the last known address of the guest or ns. For ip4.addr_seen
> we, sensibly, only update if the address we've just seen isn't 0 (0.0.0.0).
> This case can occur during early DHCP transactions.
>
> We have no equivalent case for IPv6. We're less likely to hit this,
> because DHCPv6 uses link-local addresses, however we can see an source
> address of :: with certain multicast operations. This can bite us if we
> try to make an incoming connection very early after starting pasta with
> --config-net: we may have only seen some of those multicast packets,
> updated addr_seen to :: and not had any "real" packets to update it to a
> global address. I've seen this with some of the avocado test conversions.
It looks like I haven't stared at enough packet captures yet...
> In any case, it can never make sense to update addr_seen to ::, so
> explicitly exclude that case.
>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Applied.
--
Stefano
^ permalink raw reply [flat|nested] 2+ messages in thread
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2023-05-17 19:40 ` Stefano Brivio
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