[1/1] gssd: fix handling DNS lookup failure

Commit Message

Olga Kornievskaia Oct. 4, 2023, 5:32 p.m. UTC

From: Olga Kornievskaia <[e-mail]>

When the kernel does its first ever lookup for a given server ip it
sends down info for server, protocol, etc. On the gssd side as it
scans the pipefs structure and sees a new entry it reads that info
and creates a clp_info structure. At that time it also does
a DNS lookup of the provided ip to name using getnameinfo(),
this is saved in clp->servername for all other upcalls that is
down under that directory.

IF this 1st getnameinfo() results in a failed resolution for
whatever reason (a temporary DNS resolution problem), this cause
of all other future upcalls to fail.

As a fix, this patch proposed to (1) save the server info that's
passed only in the initial pipefs new entry creation in the
clp_info structure, then (2) for the upcalls, if clp->servername
is NULL, then do the DNS lookup again and set all the needed
clp_info fields upon successful resolution.

Signed-off-by: Olga Kornievskaia <[e-mail]>
---
 utils/gssd/gssd.c | 41 +++++++++++++++++++++++++++++++++++++++++
 utils/gssd/gssd.h |  6 ++++++
 2 files changed, 47 insertions(+)

Patch

diff --git a/utils/gssd/gssd.c b/utils/gssd/gssd.c
index 833d8e01..ca9b3267 100644
--- a/utils/gssd/gssd.c
+++ b/utils/gssd/gssd.c
@@ -365,6 +365,12 @@  gssd_read_service_info(int dirfd, struct clnt_info *clp)
 
 fail:
 	printerr(0, "ERROR: failed to parse %s/info\n", clp->relpath);
+	clp->upcall_address = strdup(address);
+	clp->upcall_port = strdup(port);
+	clp->upcall_program = program;
+	clp->upcall_vers = version;
+	clp->upcall_protoname = strdup(protoname);
+	clp->upcall_service = strdup(service);
 	free(servername);
 	free(protoname);
 	clp->servicename = NULL;
@@ -408,6 +414,16 @@  gssd_free_client(struct clnt_info *clp)
 	free(clp->servicename);
 	free(clp->servername);
 	free(clp->protocol);
+	if (!clp->servername) {
+		if (clp->upcall_address)
+			free(clp->upcall_address);
+		if (clp->upcall_port)
+			free(clp->upcall_port);
+		if (clp->upcall_protoname)
+			free(clp->upcall_protoname);
+		if (clp->upcall_service)
+			free(clp->upcall_service);
+	}
 	free(clp);
 }
 
@@ -446,6 +462,31 @@  gssd_clnt_gssd_cb(int UNUSED(fd), short UNUSED(which), void *data)
 {
 	struct clnt_info *clp = data;
 
+	/* if there was a failure to translate IP to name for this server,
+	 * try again
+	 */
+	if (!clp->servername) {
+	        if (!gssd_addrstr_to_sockaddr((struct sockaddr *)&clp->addr,
+                                 clp->upcall_address, clp->upcall_port ?
+				 clp->upcall_port : "")) {
+			goto do_upcall;
+		}
+		clp->servername = gssd_get_servername(clp->upcall_address,
+				(struct sockaddr *)&clp->addr, clp->upcall_address);
+		if (!clp->servername)
+			goto do_upcall;
+
+		if (asprintf(&clp->servicename, "%s@%s", clp->upcall_service,
+					clp->servername) < 0) {
+			free(clp->servername);
+			clp->servername = NULL;
+			goto do_upcall;
+		}
+		clp->prog = clp->upcall_program;
+		clp->vers = clp->upcall_vers;
+		clp->protocol = strdup(clp->upcall_protoname);
+	}
+do_upcall:
 	handle_gssd_upcall(clp);
 }
 
diff --git a/utils/gssd/gssd.h b/utils/gssd/gssd.h
index 519dc431..4e070ed6 100644
--- a/utils/gssd/gssd.h
+++ b/utils/gssd/gssd.h
@@ -86,6 +86,12 @@  struct clnt_info {
 	int			gssd_fd;
 	struct event		*gssd_ev;
 	struct			sockaddr_storage addr;
+	char			*upcall_address;
+	char			*upcall_port;
+	int			upcall_program;
+	int			upcall_vers;
+	char			*upcall_protoname;
+	char			*upcall_service;
 };
 
 struct clnt_upcall_info {