CID 353496: Error handling issue in lib/isc/netmgr/netmgr.c

Coverity Scan finds suspicious that isc__nm_process_sock_buffer()'s return value is not being checked in lib/isc/netmgr/netmgr.c, it is elsewhere:

lib/isc/netmgr/netmgr.c:    isc__nm_process_sock_buffer(sock);
lib/isc/netmgr/tcpdns.c:        result = isc__nm_process_sock_buffer(sock);
lib/isc/netmgr/tcpdns.c:    result = isc__nm_process_sock_buffer(sock);
lib/isc/netmgr/tcpdns.c:    result = isc__nm_process_sock_buffer(csock);
lib/isc/netmgr/tlsdns.c:    result = isc__nm_process_sock_buffer(sock);
lib/isc/netmgr/tlsdns.c:                result = isc__nm_process_sock_buffer(sock);
lib/isc/netmgr/tlsdns.c:            result = isc__nm_process_sock_buffer(sock);
lib/isc/netmgr/tlsdns.c:            result = isc__nm_process_sock_buffer(sock);
lib/isc/netmgr/tlsdns.c:    result = isc__nm_process_sock_buffer(csock);

Related commit b432d5d3.

From v9_18:

*** CID 353496:  Error handling issues  (CHECKED_RETURN)
/lib/isc/netmgr/netmgr.c: 2364 in isc__nm_resume_processing()
2358     	REQUIRE(!atomic_load(&sock->client));
2359     
2360     	if (isc__nmsocket_closing(sock)) {
2361     		return;
2362     	}
2363     
>>>     CID 353496:  Error handling issues  (CHECKED_RETURN)
>>>     Calling "isc__nm_process_sock_buffer" without checking return value (as is done elsewhere 8 out of 9 times).
2364     	isc__nm_process_sock_buffer(sock);
2365     }
2366     
2367     void
2368     isc_nmhandle_cleartimeout(isc_nmhandle_t *handle) {
2369     	REQUIRE(VALID_NMHANDLE(handle));