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

Jeff Layton
2014-04-16T14:53:27Z

On Wed, 16 Apr 2014 14:03:36 +1000
NeilBrown <neilb@suse.de> 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@suse.de>
> ---
> 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@poochiereds.net>