mdns: improve numerous aspects of Posix backend

Apple's default implementation of the Posix backend for mDNSResponder
has a number of weaknesses. Address several of them, most notably:

* Improve interface tracking, preventing confusion to mdns's state
  machine. Prevents spurious removal/republication cycles whenever
  network interfaces are added or removed.

* Support network interfaces whose indeces are great than 31. Indices
  grow past that range surprisingly quickly, especially with multi-
  homed, mobile, wifi, Bluetooth, VPN, VLANs, or other interfaces
  present.

* Correctly handle edge cases during removal of a network interface.

The fixes are kept as a patch series for clarity.

Signed-off-by: Matt Hoosier <matt.hoosier@garmin.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-networking/recipes-protocols/mdns/files/0006-Remove-unneeded-function.patch

@@ -0,0 +1,51 @@
+From 157d67f152777754c059ced7511352102f23ffae Mon Sep 17 00:00:00 2001
+From: Nate Karstens <nate.karstens@garmin.com>
+Date: Mon, 24 Jul 2017 09:39:18 -0500
+Subject: [PATCH 06/11] Remove unneeded function
+
+Removes a function we no longer need by integrating it into the only
+function that calls it. This was originally separated so that we could
+only process network interfaces that netlink indicated had been changed,
+this has since been extended to test for all network intefaces.
+
+Upstream-Status: Submitted [dts@apple.com]
+
+Signed-off-by: Nate Karstens <nate.karstens@garmin.com>
+---
+ mDNSPosix/mDNSPosix.c | 13 ++-----------
+ 1 file changed, 2 insertions(+), 11 deletions(-)
+
+diff --git a/mDNSPosix/mDNSPosix.c b/mDNSPosix/mDNSPosix.c
+index 59a8b8c..3fc5451 100644
+--- a/mDNSPosix/mDNSPosix.c
++++ b/mDNSPosix/mDNSPosix.c
+@@ -1079,24 +1079,15 @@ mDNSlocal mStatus OpenIfNotifySocket(int *pFD)
+     return err;
+ }
+ 
+-mDNSlocal mDNSBool ListContainsInterfaceIndex(GenLinkedList *list, int if_index)
++mDNSlocal void AddInterfaceIndexToList(GenLinkedList *list, int if_index)
+ {
+     NetworkInterfaceIndex *item;
+ 
+     for (item = (NetworkInterfaceIndex*)list->Head; item != NULL; item = item->Next)
+     {
+-        if (if_index == item->if_index) return mDNStrue;
++        if (if_index == item->if_index) return;
+     }
+ 
+-    return mDNSfalse;
+-}
+-
+-mDNSlocal void AddInterfaceIndexToList(GenLinkedList *list, int if_index)
+-{
+-    NetworkInterfaceIndex *item;
+-
+-    if (ListContainsInterfaceIndex(list, if_index)) return;
+-
+     item = malloc(sizeof *item);
+     if (item == NULL) return;
+ 
+-- 
+2.17.1
+