mountd: prepend '$' to make use_ipaddr clients self-describing

From: "J. Bruce Fields" <bfields@redhat.com>

Mountd is responsible for filling three interrelated kernel caches:

	- auth_unix_ip maps an incoming ip addresses to a "domain".
	- nfsd_fh maps (domain, filehandle-fragment) pairs to paths.
	- nfsd_export maps (domain, path) pairs to export options.

Note that each export is assocated with a "client" string--the part
before the parentheses in an /etc/export line--which may be a domain
name, a netgroup, etc.

The "domain" string in the above three caches may be either:

	- in the !use_ipaddr case, a comma-separated list of client
	  strings.
	- in the use_ipaddr case, an ip address.

In the former case, mountd does the hard work of matching an ip address
to the clients when doing the auth_unix_ip mapping.  In the latter case,
it delays that until the nfsd_fh or nfsd_export upcall.

We're currently depending on being able to flush the kernel caches
completely when switching between the use_ipaddr and !use_ipaddr cases.
However, the kernel's cache-flushing doesn't really provide reliable
guarantees on return; it's still possible we could see nfsd_fh or
nfsd_export upcalls with the old domain-type after flushing.

So, instead, make the two domain types self-describing by prepending a
"$" in the use_ipaddr case.

Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c
index be5198e..1ae96fe 100644
--- a/utils/mountd/cache.c
+++ b/utils/mountd/cache.c
@@ -500,6 +500,8 @@ struct addrinfo *lookup_client_addr(char *dom)
 	struct addrinfo *ret;
 	struct addrinfo *tmp;
 
+	dom++; /* skip initial "$" */
+
 	tmp = host_pton(dom);
 	if (tmp == NULL)
 		return NULL;
@@ -551,7 +553,7 @@ static void nfsd_fh(FILE *f)
 
 	auth_reload();
 
-	if (use_ipaddr) {
+	if (is_ipaddr_client(dom)) {
 		ai = lookup_client_addr(dom);
 		if (!ai)
 			goto out;
@@ -587,7 +589,8 @@ static void nfsd_fh(FILE *f)
 				next_exp = exp->m_next;
 			}
 
-			if (!use_ipaddr && !namelist_client_matches(exp, dom))
+			if (!is_ipaddr_client(dom)
+					&& !namelist_client_matches(exp, dom))
 				continue;
 			if (exp->m_export.e_mountpoint &&
 			    !is_mountpoint(exp->m_export.e_mountpoint[0]?
@@ -597,7 +600,8 @@ static void nfsd_fh(FILE *f)
 
 			if (!match_fsid(&parsed, exp, path))
 				continue;
-			if (use_ipaddr && !ipaddr_client_matches(exp, ai))
+			if (is_ipaddr_client(dom)
+					&& !ipaddr_client_matches(exp, ai))
 				continue;
 			if (!found || subexport(&exp->m_export, found)) {
 				found = &exp->m_export;
@@ -1071,7 +1075,7 @@ static void nfsd_export(FILE *f)
 
 	auth_reload();
 
-	if (use_ipaddr) {
+	if (is_ipaddr_client(dom)) {
 		ai = lookup_client_addr(dom);
 		if (!ai)
 			goto out;