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nfsd: do not implicitly bind the back channel for NFSv4.1/4.2 mounts

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The NFSv4.1 (and 4.2 on 13) server incorrectly binds
a new TCP connection to the back channel when first
used by an RPC with a Sequence op in it (almost all of them).
RFC5661 specifies that only the fore channel should be bound.

This was done because early clients (including FreeBSD)
did not do the required BindConnectionToSession RPC.

Unfortunately, this breaks the Linux client when the
"nconnects" mount option is used, since the server
may do a callback on the incorrect TCP connection.

This patch converts the server behaviour to that
required by the RFC.  It also makes the server test/indicate
failure of the back channel more aggressively.

Until this patch is applied to the server, the
"nconnects" mount option is not recommended for a Linux
NFSv4.1/4.2 client mount to the FreeBSD server.

Reported by:	bcodding@redhat.com
Tested by:	bcodding@redhat.com
PR:		254560
MFC after:	1 week
This commit is contained in:
Rick Macklem 2021-03-30 14:31:05 -07:00
parent 18f3c5fe92
commit 01ae8969a9
1 changed files with 4 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
sys/fs/nfsserver/nfs_nfsdstate.c
View File

@ -6209,7 +6209,6 @@ nfsrv_checksequence(struct nfsrv_descript *nd, uint32_t sequenceid,
struct nfsdsession *sep;
struct nfssessionhash *shp;
int error;
SVCXPRT *savxprt;
shp = NFSSESSIONHASH(nd->nd_sessionid);
NFSLOCKSESSION(shp);
@ -6235,36 +6234,11 @@ nfsrv_checksequence(struct nfsrv_descript *nd, uint32_t sequenceid,
nd->nd_maxreq = sep->sess_maxreq;
nd->nd_maxresp = sep->sess_maxresp;
/*
* If this session handles the backchannel, save the nd_xprt for this
* RPC, since this is the one being used.
* RFC-5661 specifies that the fore channel will be implicitly
* bound by a Sequence operation. However, since some NFSv4.1 clients
* erroneously assumed that the back channel would be implicitly
* bound as well, do the implicit binding unless a
* BindConnectiontoSession has already been done on the session.
*/
savxprt = NULL;
if (sep->sess_clp->lc_req.nr_client != NULL &&
sep->sess_cbsess.nfsess_xprt != nd->nd_xprt &&
(sep->sess_crflags & NFSV4CRSESS_CONNBACKCHAN) != 0 &&
(sep->sess_clp->lc_flags & LCL_DONEBINDCONN) == 0) {
NFSD_DEBUG(2,
"nfsrv_checksequence: implicit back channel bind\n");
savxprt = sep->sess_cbsess.nfsess_xprt;
SVC_ACQUIRE(nd->nd_xprt);
nd->nd_xprt->xp_p2 =
sep->sess_clp->lc_req.nr_client->cl_private;
nd->nd_xprt->xp_idletimeout = 0; /* Disable timeout. */
sep->sess_cbsess.nfsess_xprt = nd->nd_xprt;
}
*sflagsp = 0;
if (sep->sess_clp->lc_req.nr_client == NULL)
if (sep->sess_clp->lc_req.nr_client == NULL ||
(sep->sess_clp->lc_flags & LCL_CBDOWN) != 0)
*sflagsp |= NFSV4SEQ_CBPATHDOWN;
NFSUNLOCKSESSION(shp);
if (savxprt != NULL)
SVC_RELEASE(savxprt);
if (error == NFSERR_EXPIRED) {
*sflagsp |= NFSV4SEQ_EXPIREDALLSTATEREVOKED;
error = 0;
@ -6464,7 +6438,8 @@ nfsrv_bindconnsess(struct nfsrv_descript *nd, uint8_t *sessionid, int *foreaftp)
nd->nd_xprt->xp_idletimeout = 0;
sep->sess_cbsess.nfsess_xprt = nd->nd_xprt;
sep->sess_crflags |= NFSV4CRSESS_CONNBACKCHAN;
clp->lc_flags |= LCL_DONEBINDCONN;
clp->lc_flags |= LCL_DONEBINDCONN |
LCL_NEEDSCBNULL;
if (*foreaftp == NFSCDFS4_BACK)
*foreaftp = NFSCDFS4_BACK;
else