A new RTF_CACHE route can be created between ip6_sk_dst_lookup_flow()
and ip6_dst_store() calls in udpv6_sendmsg(), when datagram sending
results to ICMPV6_PKT_TOOBIG error:
udp_v6_send_skb(), for example with vti6 tunnel:
vti6_xmit(), get ICMPV6_PKT_TOOBIG error
skb_dst_update_pmtu(), can create a RTF_CACHE clone
icmpv6_send()
...
udpv6_err()
ip6_sk_update_pmtu()
ip6_update_pmtu(), can create a RTF_CACHE clone
...
ip6_datagram_dst_update()
ip6_dst_store()
And after commit 33c162a980 ("ipv6: datagram: Update dst cache of
a connected datagram sk during pmtu update"), the UDPv6 error handler
can update socket's dst cache, but it can happen before the update in
the end of udpv6_sendmsg(), preventing getting the new dst cache on
the next udpv6_sendmsg() calls.
In order to fix it, save dst in a connected socket only if the current
socket's dst cache is invalid.
The previous patch prepared ip6_sk_dst_lookup_flow() to do that with
the new argument, and this patch enables it in udpv6_sendmsg().
Fixes: 33c162a980 ("ipv6: datagram: Update dst cache of a connected datagram sk during pmtu update")
Fixes: 45e4fd2668 ("ipv6: Only create RTF_CACHE routes after encountering pmtu exception")
Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
4f858c56bd