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

NeilBrown
2014-04-16T23:25:22Z

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On Wed, 16 Apr 2014 10:47:02 -0400 Jeff Layton <jlayton@poochiereds.net>
wrote:

> 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.

I was hoping someone on net-dev would have commented if it didn't work - I
probably should have explicitly asked.

My testing certainly suggests that this works if I use any local address to
perform the mount, not just 127.0.0.1.
I don't know enough about routing and neighbours and the dst cache to be
certain but my shallow understanding was always that traffic to any local
address was pseudo-routed through the lo interface and would never get
anywhere near e.g. the eth0 interface.

Can any network people confirm?

Thanks,
NeilBrown

>
>
> > 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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>
>

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