Fix an SNMP bug in the IPP backend.

Author: michaelrsweet

CHANGES.md

@@ -30,6 +30,8 @@ Changes in CUPS v2.4.17 (YYYY-MM-DD)
 - Fixed possible use-after-free in `cupsdReadClient()` (Issue #1454)
 - Fixed a document format bug in the IPP backend (Issue #1457)
 - Fixed a bug when then `ippFindXxx` and `ippSetXxx` functions were mixed.
+- Fixed the mapping of supply type keywords to SNMP names.
+- Fixed a bug in the IPP backend when SNMP was disabled.
 
 
 Changes in CUPS v2.4.16 (2025-12-04)

backend/ipp.c

@@ -1698,13 +1698,14 @@ main(int  argc,				/* I - Number of command-line args */
 
           FD_ZERO(&input);
 	  FD_SET(fd, &input);
-	  FD_SET(snmp_fd, &input);
+	  if (snmp_fd >= 0)
+	    FD_SET(snmp_fd, &input);
 	  FD_SET(CUPS_SC_FD, &input);
 
           while (select(fd > snmp_fd ? fd + 1 : snmp_fd + 1, &input, NULL, NULL,
 	                NULL) <= 0 && !job_canceled);
 
-	  if (FD_ISSET(snmp_fd, &input))
+	  if (snmp_fd >= 0 && FD_ISSET(snmp_fd, &input))
 	    backendCheckSideChannel(snmp_fd, http->hostaddr);
 
           if (FD_ISSET(fd, &input))