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>

1 files changed, 58 insertions, 0 deletions

diff --git a/meta-networking/recipes-protocols/mdns/files/0002-Create-subroutine-for-tearing-down-an-interface.patch b/meta-networking/recipes-protocols/mdns/files/0002-Create-subroutine-for-tearing-down-an-interface.patch
new file mode 100644
index 0000000000..21ba318499
--- /dev/null
+++ b/meta-networking/recipes-protocols/mdns/files/0002-Create-subroutine-for-tearing-down-an-interface.patch
@@ -0,0 +1,58 @@
+From a2148df99ddcd122247f95c4cbcce5c4118581a1 Mon Sep 17 00:00:00 2001
+From: Nate Karstens <nate.karstens@garmin.com>
+Date: Wed, 28 Jun 2017 17:30:00 -0500
+Subject: [PATCH 02/11] Create subroutine for tearing down an interface
+
+Creates a subroutine for tearing down an interface.
+
+Upstream-Status: Submitted [dts@apple.com]
+
+Signed-off-by: Nate Karstens <nate.karstens@garmin.com>
+---
+ mDNSPosix/mDNSPosix.c | 22 ++++++++++++++++------
+ 1 file changed, 16 insertions(+), 6 deletions(-)
+
+diff --git a/mDNSPosix/mDNSPosix.c b/mDNSPosix/mDNSPosix.c
+index ffc9696..5e5b2cd 100644
+--- a/mDNSPosix/mDNSPosix.c
++++ b/mDNSPosix/mDNSPosix.c
+@@ -591,6 +591,19 @@ mDNSlocal void FreePosixNetworkInterface(PosixNetworkInterface *intf)
+     gRecentInterfaces = intf;
+ }
+ 
++mDNSlocal void TearDownInterface(mDNS *const m, PosixNetworkInterface *intf)
++{
++    mDNS_DeregisterInterface(m, &intf->coreIntf, NormalActivation);
++    if (gMDNSPlatformPosixVerboseLevel > 0) fprintf(stderr, "Deregistered interface %s\n", intf->intfName);
++    FreePosixNetworkInterface(intf);
++
++    num_registered_interfaces--;
++    if (num_registered_interfaces == 0) {
++        num_pkts_accepted = 0;
++        num_pkts_rejected = 0;
++    }
++}
++
+ // Grab the first interface, deregister it, free it, and repeat until done.
+ mDNSlocal void ClearInterfaceList(mDNS *const m)
+ {
+@@ -599,13 +612,10 @@ mDNSlocal void ClearInterfaceList(mDNS *const m)
+     while (m->HostInterfaces)
+     {
+         PosixNetworkInterface *intf = (PosixNetworkInterface*)(m->HostInterfaces);
+-        mDNS_DeregisterInterface(m, &intf->coreIntf, NormalActivation);
+-        if (gMDNSPlatformPosixVerboseLevel > 0) fprintf(stderr, "Deregistered interface %s\n", intf->intfName);
+-        FreePosixNetworkInterface(intf);
++        TearDownInterface(m, intf);
+     }
+-    num_registered_interfaces = 0;
+-    num_pkts_accepted = 0;
+-    num_pkts_rejected = 0;
++
++    assert(num_registered_interfaces == 0);
+ }
+ 
+ // Sets up a send/receive socket.
+-- 
+2.17.1
+