Fix mDNS support for network printers.

At least on FreeBSD 13, SO_REUSEPORT is no longer sufficient when Avahi
already uses port 5353.  It seems that port reuse is only allowed for
processes from the same user now.  But even if Avahi is not running and
port 5353 is available my printer still failed to be detected.  According
to RFC 6762 only fully compliant queriers should be using that port which
HPLIP isn't.  I suspect the printer is sending responses that HPLIP can't
parse.  Patch HPLIP to use a simple socket (dynamically allocated port)
which is enough for the one-shot mDNS queries it performs.

Now my printer is detected by "hp-probe --method=mdns" and xsane can find
the scanner part using the hpaio plugin.

PR:		247723
Approved by:	maintainer timeout (19 days)

2 files changed, 70 insertions, 11 deletions

diff --git a/print/hplip/Makefile b/print/hplip/Makefile
index 91da432be3fe..0a1e818e9ffd 100644
--- a/print/hplip/Makefile
+++ b/print/hplip/Makefile
@@ -3,7 +3,7 @@
 
 PORTNAME=	hplip
 PORTVERSION=	3.20.3
-PORTREVISION=	0
+PORTREVISION=	1
 CATEGORIES=	print
 MASTER_SITES=	SF
 
diff --git a/print/hplip/files/patch-protocol_discovery_mdns.c b/print/hplip/files/patch-protocol_discovery_mdns.c
index 06c2bbfca10d..f22417a63aa3 100644
--- a/print/hplip/files/patch-protocol_discovery_mdns.c
+++ b/print/hplip/files/patch-protocol_discovery_mdns.c
@@ -1,4 +1,16 @@
---- protocol/discovery/mdns.c.orig	2019-10-22 06:18:12 UTC
+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
@@ -13,15 +25,62 @@
  #include <string.h>
  #include <syslog.h>
  #include <sys/socket.h>
-@@ -85,6 +89,11 @@ static int mdns_open_socket(int *psocket)
+@@ -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;
  
-     /* 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;
-+    }
-+    if (setsockopt(udp_socket, SOL_SOCKET, SO_REUSEPORT, &yes, sizeof(yes)) == -1)
+     DBG("mdns_open_socket entry.\n");
+ 
+     if ((udp_socket = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
      {
-         BUG("unable to setsockopt: %m\n");
+         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;
+     }
+