netdev - Re: [PATCH 1/2] ipvs: load balance IPv4 connections from a local process

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Date:	Fri, 5 Sep 2008 08:49:52 +0300 (EEST)
From:	Siim Põder <siim@...rad-teel.net>
To:	"Julian Anastasov" <ja@....bg>
Cc:	"Simon Horman" <horms@...ge.net.au>, netdev@...r.kernel.org,
	lvs-devel@...r.kernel.org,
	"Malcolm Turnbull" <malcolm@...dbalancer.org>,
	Siim Põder <siim@...rad-teel.net>,
	"Julius Volz" <juliusv@...gle.com>,
	"Vince Busam" <vbusam@...gle.com>
Subject: Re: [PATCH 1/2] ipvs: load balance IPv4 connections from a local 
     process

Hi

> 	TCP checksum is not optional, why this change appeared?

The new packets that we handle are on the loopback device and no checksums
appear to be generated there. I initially changed the condition to check
for loopback device (which we could do), but checking udp code found that
it already handled it by checking zero checksum, hence the same
implementation in tcp code.

>> Index: lvs-2.6/net/ipv4/ipvs/ip_vs_proto_tcp.c
>> ===================================================================
>> --- lvs-2.6.orig/net/ipv4/ipvs/ip_vs_proto_tcp.c	2008-09-03
>> 10:56:05.000000000 +1000
>> +++ lvs-2.6/net/ipv4/ipvs/ip_vs_proto_tcp.c	2008-09-03
>> 11:24:26.000000000 +1000
>> @@ -166,7 +166,7 @@ tcp_snat_handler(struct sk_buff *skb,
>>  	tcph->source = cp->vport;
>>
>>  	/* Adjust TCP checksums */
>> -	if (!cp->app) {
>> +	if (!cp->app && (tcph->check != 0)) {
>>  		/* Only port and addr are changed, do fast csum update */
>>  		tcp_fast_csum_update(cp->af, tcph, &cp->daddr, &cp->vaddr,
>>  				     cp->dport, cp->vport);
>> @@ -235,7 +235,7 @@ tcp_dnat_handler(struct sk_buff *skb,
>>  	/*
>>  	 *	Adjust TCP checksums
>>  	 */
>> -	if (!cp->app) {
>> +	if (!cp->app && (tcph->check != 0)) {
>>  		/* Only port and addr are changed, do fast csum update */
>>  		tcp_fast_csum_update(cp->af, tcph, &cp->vaddr, &cp->daddr,
>>  				     cp->vport, cp->dport);
>> --

-- 
Siiralt Teie,
Elektromehaaniline Põder

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