[PATCH] Fill in rqstp->rq_daddr in svc_tcp_recvfrom

[PATCH] Fill in rqstp->rq_daddr in svc_tcp_recvfrom

[Olaf Kirch]

Here's a patch we added to SLES in response to a customer bug report:

# Subject: Fill in rqstp->rq_daddr in svc_tcp_recvfrom
#
# This patch fills the daddr member of the rpc struct svc_rqst structure for  
# TCP-based sockets in the recvfrom proceedure.  Currently, the field is 
# not set thus leaving it with left over garbage from a previous allocation. 
#
# This makes the behavior consistent between UDP- and TCP-based RPC. 
#
# This patch enables HA software to failover TCP-based RPC services
# such as TCP-based NFS. 
#
# Signed-off-by: okir@suse.de

Index: linux-2.6.12.orig/net/sunrpc/svcsock.c
===================================================================
--- linux-2.6.12.orig/net/sunrpc/svcsock.c	2005-07-08 11:45:25.000000000 +0200
+++ linux-2.6.12/net/sunrpc/svcsock.c	2005-07-12 10:57:05.000000000 +0200
@@ -455,8 +455,9 @@ svc_recvfrom(struct svc_rqst *rqstp, str
 	struct socket	*sock;
 	int		len, alen;
 
-	rqstp->rq_addrlen = sizeof(rqstp->rq_addr);
 	sock = rqstp->rq_sock->sk_sock;
+	rqstp->rq_daddr = inet_sk((const struct sock *)sock)->rcv_saddr;
+	rqstp->rq_addrlen = sizeof(rqstp->rq_addr);
 
 	msg.msg_name    = &rqstp->rq_addr;
 	msg.msg_namelen = sizeof(rqstp->rq_addr);
-- 
Olaf Kirch   |  --- o --- Nous sommes du soleil we love when we play
okir@suse.de |    / | \   sol.dhoop.naytheet.ah kin.ir.samse.qurax


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Re: [PATCH] Fill in rqstp->rq_daddr in svc_tcp_recvfrom

[J. Bruce Fields]

On Tue, Jul 12, 2005 at 11:04:56AM +0200, Olaf Kirch wrote:
> Here's a patch we added to SLES in response to a customer bug report:
> 
> # Subject: Fill in rqstp->rq_daddr in svc_tcp_recvfrom
> #
> # This patch fills the daddr member of the rpc struct svc_rqst structure for  
> # TCP-based sockets in the recvfrom proceedure.  Currently, the field is 
> # not set thus leaving it with left over garbage from a previous allocation. 
> #
> # This makes the behavior consistent between UDP- and TCP-based RPC. 
> #
> # This patch enables HA software to failover TCP-based RPC services
> # such as TCP-based NFS.

Could you explain how this patch makes a difference?  I can only see the
value of rq_daddr used in one place, in svc_sendto:
        if (rqstp->rq_prot == IPPROTO_UDP) {
...
                pki->ipi_spec_dst.s_addr = rqstp->rq_daddr;

                if (sock_sendmsg(sock, &msg, 0) < 0)
                        goto out;
        }

So it doesn't seem to be used at all in the TCP case.  Am I confused?

--b.


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Re: [PATCH] Fill in rqstp->rq_daddr in svc_tcp_recvfrom

[Olaf Kirch]

Hi Bruce,

> Could you explain how this patch makes a difference?  I can only see the
> value of rq_daddr used in one place, in svc_sendto:

It doesn't make a difference for the existing RPC users, but the customer
had some kernel RPC code of their own (I think some HA capable nfsd)
that needed this information for migration/failover.

It's not strictly necessary, but it doesn't hurt either - and it makes
sense in the way that UDP and TCP now fill in the same set of information.

Olaf
-- 
Olaf Kirch   |  --- o --- Nous sommes du soleil we love when we play
okir@suse.de |    / | \   sol.dhoop.naytheet.ah kin.ir.samse.qurax


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Re: [PATCH] Fill in rqstp->rq_daddr in svc_tcp_recvfrom

[Christoph Hellwig]

On Wed, Jul 13, 2005 at 07:17:50AM +0200, Olaf Kirch wrote:
> Hi Bruce,
> 
> > Could you explain how this patch makes a difference?  I can only see the
> > value of rq_daddr used in one place, in svc_sendto:
> 
> It doesn't make a difference for the existing RPC users, but the customer
> had some kernel RPC code of their own (I think some HA capable nfsd)
> that needed this information for migration/failover.

So let the customer post the patch, including the code that uses it,
as that might actually be useful for others aswell.



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