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Use a dynamically allocated port instead of binding port 5353. The bind(2)
call fails when Avahi has already claimed port 5353. On top of that, HPLIP
only performs one-shot queries and those shouldn't be using port 5353 according
to RFC 6762.
Don't disable loop-back. It's harmless.
Use default TTL of 1. RFC 6762 requires 255 for responses, not for queries.
There's no need to join the multicast group for one-shot queries. Responses
are sent to the unicast address.
--- protocol/discovery/mdns.c.orig 2020-07-01 14:48:56 UTC
+++ protocol/discovery/mdns.c
@@ -24,7 +24,11 @@
Author: Sanjay Kumar
\*****************************************************************************/
-//#include <stdio.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/select.h>
#include <string.h>
#include <syslog.h>
#include <sys/socket.h>
@@ -70,57 +74,13 @@ static int mdns_convert_name_to_dns(const char *name,
static int mdns_open_socket(int *psocket)
{
int stat = MDNS_STATUS_ERROR;
- int udp_socket = -1, yes = 1;
- char loop = 0, ttl = 255;
- struct sockaddr_in recv_addr , addr;
- struct ip_mreq mreq;
+ int udp_socket;
DBG("mdns_open_socket entry.\n");
if ((udp_socket = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
{
BUG("unable to create udp socket: %m\n");
- goto bugout;
- }
-
- /* Get rid of "address already in use" error message. */
- if (setsockopt(udp_socket, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)) == -1)
- {
- BUG("unable to setsockopt: %m\n");
- goto bugout;
- }
-
- /* Bind the socket to port and IP equal to INADDR_ANY. */
- bzero(&recv_addr, sizeof(recv_addr));
- recv_addr.sin_family = AF_INET;
- recv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
- recv_addr.sin_port = htons(5353);
- if (bind(udp_socket, (struct sockaddr *) &recv_addr, sizeof(recv_addr)) == -1)
- {
- BUG("unable to bind udp socket: %m\n");
- goto bugout;
- }
-
- /* Set multicast loopback off. */
- if (setsockopt(udp_socket, IPPROTO_IP, IP_MULTICAST_LOOP, &loop, sizeof(loop)) == -1)
- {
- BUG("unable to setsockopt: %m\n");
- goto bugout;
- }
-
- /* Set ttl to 255. Required by mdns. */
- if (setsockopt(udp_socket, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl))== -1)
- {
- BUG("unable to setsockopt: %m\n");
- goto bugout;
- }
-
- /* Join the .local multicast group */
- mreq.imr_multiaddr.s_addr = inet_addr("224.0.0.251");
- mreq.imr_interface.s_addr = htonl(INADDR_ANY);
- if (setsockopt(udp_socket, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(struct ip_mreq)) == -1) {
- BUG("unable to add to multicast group: %m\n");
- close(udp_socket);
goto bugout;
}
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