From: weidong <[EMAIL PROTECTED]>
Date: Wed, 14 Feb 2007 10:03:49 -0500
> Hi, All
> When I tested Linux-2.6.20 and found that counter "ipOutNoRoutes" can
> not increase correctly.
> The criteria is RFC2011
>
> ipOutNoRoutes OBJECT-TYPE
> SYNTAX Counter32
> MAX-ACCESS read-only
> STATUS current
> DESCRIPTION
> "The number of IP datagrams discarded because no route could
> be found to transmit them to their destination. Note that
> this counter includes any packets counted in ipForwDatagrams
> which meet this `no-route' criterion. Note that this
> includes any datagrams which a host cannot route because all
> of its default routers are down."
> ::= { ip 12 }
>
> In current Linux TCP/IP stack, maybe we should not increase this counter
> in "input path", but only increase it in "output path" due to the TCP/IP
> stack performance.
>
> Now in "output path", when TCP client tries to connect to an unreachable
> server(net unreachable, so no route can be found), this counter has no
> increment. When we use UDP sending UDP datagram to an net unreachable
> address, this counter also has no increment.
>
> Function need to fix:
> tcp_v4_connect(); ip4_datagram_connect(); udp_sendmsg();
>
> The following patch can fix the problems mentioned above
Thank you for this patch.
I think we need to make these checks more carefully.
Route lookup can fail for several reasons other than
no route being available. Two examples are:
1) Out of memory error while creating route
2) IPSEC disallows communication to that flow ID
As a result, we'll probably best limiting the counter
increment when the error is either -EHOSTUNREACH or
-ENETUNREACH.
Probably, since this logic will be duplicated to several
locations, you'll want to implement the test inside of
a helper inline function.
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