[PATCH v1 6/7] sunrpc: preserve rq_daddrlen across request deferral

[Chuck Lever <cel@kernel.org>]

svc_defer() saves rq_daddr in the svc_deferred_req but not
rq_daddrlen, and svc_deferred_recv() restores only the address. The
thread that replays a deferred request keeps the rq_daddrlen of the
last request it processed. A newly created thread has a length of
zero.

gen_callback() and nlmsvc_lookup_host() copy rq_daddrlen bytes of
rq_daddr to form the source address of an NFSv4.0 or NLM callback
transport. When a new thread replays a deferred SETCLIENTID that
arrived over IPv6, the copy is empty and the source address is left
as AF_UNSPEC. xs_bind() then fails with -EAFNOSUPPORT, and the
callback transport never connects. A length left over from an IPv4
request copies only part of an IPv6 address. Found by code
inspection.

Record rq_daddrlen in the existing daddrlen field of struct
svc_deferred_req when the request is first deferred, and restore it
in svc_deferred_recv().

Fixes: 849a1cf13d43 ("SUNRPC: Replace svc_addr_u by sockaddr_storage")
Signed-off-by: Chuck Lever <cel@kernel.org>
---
 net/sunrpc/svc_xprt.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index bf5b2cdad35e..031cbac2a612 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -1343,6 +1343,7 @@ static struct cache_deferred_req *svc_defer(struct cache_req *req)
 		memcpy(&dr->addr, &rqstp->rq_addr, rqstp->rq_addrlen);
 		dr->addrlen = rqstp->rq_addrlen;
 		dr->daddr = rqstp->rq_daddr;
+		dr->daddrlen = rqstp->rq_daddrlen;
 		dr->secure = test_bit(RQ_SECURE, &rqstp->rq_flags);
 		dr->argslen = rqstp->rq_arg.len >> 2;
 
@@ -1377,6 +1378,7 @@ static noinline int svc_deferred_recv(struct svc_rqst *rqstp)
 	memcpy(&rqstp->rq_addr, &dr->addr, dr->addrlen);
 	rqstp->rq_addrlen     = dr->addrlen;
 	rqstp->rq_daddr       = dr->daddr;
+	rqstp->rq_daddrlen    = dr->daddrlen;
 	rqstp->rq_xprt_ctxt   = dr->xprt_ctxt;
 	/*
 	 * ->xpo_recvfrom() is bypassed for a deferred request, so the
-- 
2.55.0