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Re: [PATCH 05/19] SUNRPC: track whether a request is coming from a loop-

To: NeilBrown <neilb@xxxxxxx>
Subject: Re: [PATCH 05/19] SUNRPC: track whether a request is coming from a loop-back interface.
From: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
Date: Wed, 16 Apr 2014 10:47:02 -0400
Cc: linux-mm@xxxxxxxxx, linux-nfs@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140416040336.10604.14822.stgit@xxxxxxxxxxxxxx>
References: <20140416033623.10604.69237.stgit@xxxxxxxxxxxxxx> <20140416040336.10604.14822.stgit@xxxxxxxxxxxxxx>
On Wed, 16 Apr 2014 14:03:36 +1000
NeilBrown <neilb@xxxxxxx> wrote:

> If an incoming NFS request is coming from the local host, then
> nfsd will need to perform some special handling.  So detect that
> possibility and make the source visible in rq_local.
> 
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
> ---
>  include/linux/sunrpc/svc.h      |    1 +
>  include/linux/sunrpc/svc_xprt.h |    1 +
>  net/sunrpc/svcsock.c            |   10 ++++++++++
>  3 files changed, 12 insertions(+)
> 
> diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
> index 04e763221246..a0dbbd1e00e9 100644
> --- a/include/linux/sunrpc/svc.h
> +++ b/include/linux/sunrpc/svc.h
> @@ -254,6 +254,7 @@ struct svc_rqst {
>       u32                     rq_prot;        /* IP protocol */
>       unsigned short
>                               rq_secure  : 1; /* secure port */
> +     unsigned short          rq_local   : 1; /* local request */
>  
>       void *                  rq_argp;        /* decoded arguments */
>       void *                  rq_resp;        /* xdr'd results */
> diff --git a/include/linux/sunrpc/svc_xprt.h b/include/linux/sunrpc/svc_xprt.h
> index b05963f09ebf..b99bdfb0fcf9 100644
> --- a/include/linux/sunrpc/svc_xprt.h
> +++ b/include/linux/sunrpc/svc_xprt.h
> @@ -63,6 +63,7 @@ struct svc_xprt {
>  #define      XPT_DETACHED    10              /* detached from tempsocks list 
> */
>  #define XPT_LISTENER 11              /* listening endpoint */
>  #define XPT_CACHE_AUTH       12              /* cache auth info */
> +#define XPT_LOCAL    13              /* connection from loopback interface */
>  
>       struct svc_serv         *xpt_server;    /* service for transport */
>       atomic_t                xpt_reserved;   /* space on outq that is rsvd */
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index b6e59f0a9475..193115fe968c 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -811,6 +811,7 @@ static struct svc_xprt *svc_tcp_accept(struct svc_xprt 
> *xprt)
>       struct socket   *newsock;
>       struct svc_sock *newsvsk;
>       int             err, slen;
> +     struct dst_entry *dst;
>       RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);
>  
>       dprintk("svc: tcp_accept %p sock %p\n", svsk, sock);
> @@ -867,6 +868,14 @@ static struct svc_xprt *svc_tcp_accept(struct svc_xprt 
> *xprt)
>       }
>       svc_xprt_set_local(&newsvsk->sk_xprt, sin, slen);
>  
> +     clear_bit(XPT_LOCAL, &newsvsk->sk_xprt.xpt_flags);
> +     rcu_read_lock();
> +     dst = rcu_dereference(newsock->sk->sk_dst_cache);
> +     if (dst && dst->dev &&
> +         (dst->dev->features & NETIF_F_LOOPBACK))
> +             set_bit(XPT_LOCAL, &newsvsk->sk_xprt.xpt_flags);
> +     rcu_read_unlock();
> +

In the use-case you describe, the client is unlikely to have mounted
"localhost", but is more likely to be mounting a floating address in
the cluster.

Will this flag end up being set in such a situation? It looks like
NETIF_F_LOOPBACK isn't set on all adapters -- mostly on "lo" and a few
others that support MAC-LOOPBACK.


>       if (serv->sv_stats)
>               serv->sv_stats->nettcpconn++;
>  
> @@ -1112,6 +1121,7 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
>  
>       rqstp->rq_xprt_ctxt   = NULL;
>       rqstp->rq_prot        = IPPROTO_TCP;
> +     rqstp->rq_local       = !!test_bit(XPT_LOCAL, &svsk->sk_xprt.xpt_flags);
>  
>       p = (__be32 *)rqstp->rq_arg.head[0].iov_base;
>       calldir = p[1];
> 
> 
> --
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-- 
Jeff Layton <jlayton@xxxxxxxxxxxxxxx>

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