29 Nov
2010
29 Nov
'10
3:14 p.m.
On 11/29/2010 02:16 PM, Iñaki Baz Castillo wrote:
2010/11/29 marius
zbihlei<marius.zbihlei(a)1and1.ro>ro>:
Possible, but not easily implementable, as ICMP Host unreachable are
sent asynchronously from the kernel. Also the current sendto() call does
not guarantee delivery on all Unixes (Linux should be fine), connected
UDP sockets are to be used instead.
Kamailio does not use ICMP replies to check if a
host is reachable on a UDP
sendto(). This means that ICMP port unreachable errors are not handled by K
and so the same host is retried on TM retransmits.
AFAIR using raw sockets checking ICMP notifications would be possible
(not yet implemented, but possible as I remember from a thread with
Andrei).
IMHO this would be very useful because if a UDP port
is unreachable
and there is a ICMP notification about it, the proxy should generate
an internal 503 (transport error) rather than a 408 (fr_timer
timeout).
Well, this means that we should disable dns_failover (or equivalents)
completely and handle ICMP errors in failure_route blocks(just test if
the transaction issued a 503). If I recall RFC 3263 , this would mean
another server discovery (as the new request generates a new
transaction) so again there is the possibility that the broken host is
selected. If we use this dns fallback(IMHO this is a nice feature- I
personally rely on this) how do we decide to generate a 503 ?
If the host is already a IP address, that it would be ok to send a 503,
as no DNS failover is possible.
Ideas?
Marius