I have a small-to-medium net here and I refer to my internal hosts by IPs,
not names.
Unexpectedly, when external link to Inet is down, NFS mounts are slow.
I didn't expect mountd to use DNS at all if all hosts in /etc/exports
are referred with numeric IP addresses, but it does use DNS.
Narrowing it down, I edited resolv.conf in order to direct DNS queries
to non-existing host, removed 127.0.0.1 localhost from /etc/hosts
and NFS mounts did not work at all.
# cat /etc/exports
# See exports(5) for a description.
# This file contains a list of all directories exported to other computers.
# It is used by rpc.nfsd and rpc.mountd.
/ 127.0.0.1(rw,no_root_squash,async)
This is what happens when I try to mount 127.0.0.1:/ (log of instrumented mountd):
11:04:15 rpc.mountd: MNT3(/) calledd
11:04:15 rpc.mountd: get_rootfh() start
11:04:15 rpc.mountd: get_rootfh() 1
11:04:15 rpc.mountd: get_rootfh() 2
11:04:15 rpc.mountd: auth_authenticate(): get_reliable_hostbyaddr start
11:04:15 rpc.mountd: get_reliable_hostbyaddr(): gethostbyaddr start
here DNS requests time out...
11:04:25 rpc.mountd: get_reliable_hostbyaddr(): gethostbyaddr finish
11:04:25 rpc.mountd: auth_authenticate(): get_reliable_hostbyaddr finish
11:04:25 rpc.mountd: auth_authenticate(): get_hostent start
11:04:25 rpc.mountd: auth_authenticate(): get_hostent finish
11:04:25 rpc.mountd: mount request from unknown host 127.0.0.1 for / (/)
Any suggestions how to properly fix it?
Relevant part of nfsutils-1.0.7 utils/mountd/auth.c
is below sig (instrumentation not shown).
Code flow:
get_reliable_hostbyaddr (DNS timeount) -> get_hostent ->
-> while(1){...} -> switch (error){ ->
-> case unknown_host: -> "mount request from unknown host..."
--
vda
hp = get_reliable_hostbyaddr((const char*)&caller->sin_addr, sizeof(struct in_addr),
AF_INET);
if (!hp)
hp = get_hostent((const char*)&caller->sin_addr, sizeof(struct in_addr),
AF_INET);
if (!hp)
return exp;
/* Try the longest matching exported pathname. */
while (1) {
exp = auth_authenticate_internal(what, caller, epath,
hp, &error);
if (exp || (error != not_exported && error != no_entry))
break;
/* We have to treat the root, "/", specially. */
if (p == &epath[1]) break;
p = strrchr(epath, '/');
if (p == epath) p++;
*p = '\0';
}
switch (error) {
case bad_path:
xlog(L_WARNING, "bad path in %s request from %s: \"%s\"",
what, inet_ntoa(addr), path);
break;
case unknown_host:
xlog(L_WARNING, "%s request from unknown host %s for %s (%s)",
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