From e79f81f5cd626ad77ec64de4325f6645cf253c5e Mon Sep 17 00:00:00 2001
From: Nate Karstens <nate.karstens@garmin.com>
Date: Thu, 13 Jul 2017 09:00:00 -0500
Subject: [PATCH 5/8] Use list for changed interfaces

Uses a linked list to store the index of changed network interfaces
instead of a bitfield. This allows for network interfaces with an
index greater than 31 (an index of 36 was seen on Android).

Upstream-Status: Submitted [dts@apple.com]

Signed-off-by: Nate Karstens <nate.karstens@garmin.com>
Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
---
 mDNSPosix/mDNSPosix.c | 58 ++++++++++++++++++++++++++++++++-----------
 1 file changed, 43 insertions(+), 15 deletions(-)

diff --git a/mDNSPosix/mDNSPosix.c b/mDNSPosix/mDNSPosix.c
index 02a19b438e03..e20adda92229 100644
--- a/mDNSPosix/mDNSPosix.c
+++ b/mDNSPosix/mDNSPosix.c
@@ -74,6 +74,14 @@ struct IfChangeRec
 };
 typedef struct IfChangeRec IfChangeRec;
 
+// Used to build a list of network interface indices
+struct NetworkInterfaceIndex
+{
+    int if_index;
+    struct NetworkInterfaceIndex *Next;
+};
+typedef struct NetworkInterfaceIndex NetworkInterfaceIndex;
+
 // Note that static data is initialized to zero in (modern) C.
 static PosixEventSource *gEventSources;             // linked list of PosixEventSource's
 static sigset_t gEventSignalSet;                // Signals which event loop listens for
@@ -1621,6 +1629,23 @@ mDNSlocal mStatus OpenIfNotifySocket(int *pFD)
     return err;
 }
 
+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;
+    }
+
+    item = mdns_malloc(sizeof *item);
+    if (item == NULL) return;
+
+    item->if_index = if_index;
+    item->Next = NULL;
+    AddToTail(list, item);
+}
+
 #if MDNS_DEBUGMSGS
 mDNSlocal void      PrintNetLinkMsg(const struct nlmsghdr *pNLMsg)
 {
@@ -1648,14 +1673,13 @@ mDNSlocal void      PrintNetLinkMsg(const struct nlmsghdr *pNLMsg)
 }
 #endif
 
-mDNSlocal mDNSu32       ProcessRoutingNotification(int sd)
+mDNSlocal void          ProcessRoutingNotification(int sd, GenLinkedList *changedInterfaces)
 // Read through the messages on sd and if any indicate that any interface records should
 // be torn down and rebuilt, return affected indices as a bitmask. Otherwise return 0.
 {
     ssize_t readCount;
     char buff[4096];
     struct nlmsghdr         *pNLMsg = (struct nlmsghdr*) buff;
-    mDNSu32 result = 0;
 
     // The structure here is more complex than it really ought to be because,
     // unfortunately, there's no good way to size a buffer in advance large
@@ -1691,9 +1715,9 @@ mDNSlocal mDNSu32       ProcessRoutingNotification(int sd)
 
         // Process the NetLink message
         if (pNLMsg->nlmsg_type == RTM_GETLINK || pNLMsg->nlmsg_type == RTM_NEWLINK)
-            result |= 1 << ((struct ifinfomsg*) NLMSG_DATA(pNLMsg))->ifi_index;
+            AddInterfaceIndexToList(changedInterfaces, ((struct ifinfomsg*) NLMSG_DATA(pNLMsg))->ifi_index);
         else if (pNLMsg->nlmsg_type == RTM_DELADDR || pNLMsg->nlmsg_type == RTM_NEWADDR)
-            result |= 1 << ((struct ifaddrmsg*) NLMSG_DATA(pNLMsg))->ifa_index;
+            AddInterfaceIndexToList(changedInterfaces, ((struct ifaddrmsg*) NLMSG_DATA(pNLMsg))->ifa_index);
 
         // Advance pNLMsg to the next message in the buffer
         if ((pNLMsg->nlmsg_flags & NLM_F_MULTI) != 0 && pNLMsg->nlmsg_type != NLMSG_DONE)
@@ -1704,8 +1728,6 @@ mDNSlocal mDNSu32       ProcessRoutingNotification(int sd)
         else
             break;  // all done!
     }
-
-    return result;
 }
 
 #else // USES_NETLINK
@@ -1737,14 +1759,13 @@ mDNSlocal void      PrintRoutingSocketMsg(const struct ifa_msghdr *pRSMsg)
 }
 #endif
 
-mDNSlocal mDNSu32       ProcessRoutingNotification(int sd)
+mDNSlocal void          ProcessRoutingNotification(int sd, GenLinkedList *changedInterfaces)
 // Read through the messages on sd and if any indicate that any interface records should
 // be torn down and rebuilt, return affected indices as a bitmask. Otherwise return 0.
 {
     ssize_t readCount;
     char buff[4096];
     struct ifa_msghdr       *pRSMsg = (struct ifa_msghdr*) buff;
-    mDNSu32 result = 0;
 
     readCount = read(sd, buff, sizeof buff);
     if (readCount < (ssize_t) sizeof(struct ifa_msghdr))
@@ -1759,12 +1780,10 @@ mDNSlocal mDNSu32       ProcessRoutingNotification(int sd)
         pRSMsg->ifam_type == RTM_IFINFO)
     {
         if (pRSMsg->ifam_type == RTM_IFINFO)
-            result |= 1 << ((struct if_msghdr*) pRSMsg)->ifm_index;
+            AddInterfaceIndexToList(changedInterfaces, ((struct if_msghdr*) pRSMsg)->ifm_index);
         else
-            result |= 1 << pRSMsg->ifam_index;
+            AddInterfaceIndexToList(changedInterfaces, pRSMsg->ifam_index);
     }
-
-    return result;
 }
 
 #endif // USES_NETLINK
@@ -1774,7 +1793,8 @@ mDNSlocal void InterfaceChangeCallback(int fd, void *context)
 {
     IfChangeRec     *pChgRec = (IfChangeRec*) context;
     fd_set readFDs;
-    mDNSu32 changedInterfaces = 0;
+    GenLinkedList changedInterfaces;
+    NetworkInterfaceIndex *changedInterface;
     struct timeval zeroTimeout = { 0, 0 };
 
     (void)fd; // Unused
@@ -1782,17 +1802,25 @@ mDNSlocal void InterfaceChangeCallback(int fd, void *context)
     FD_ZERO(&readFDs);
     FD_SET(pChgRec->NotifySD, &readFDs);
 
+    InitLinkedList(&changedInterfaces, offsetof(NetworkInterfaceIndex, Next));
+
     do
     {
-        changedInterfaces |= ProcessRoutingNotification(pChgRec->NotifySD);
+        ProcessRoutingNotification(pChgRec->NotifySD, &changedInterfaces);
     }
     while (0 < select(pChgRec->NotifySD + 1, &readFDs, (fd_set*) NULL, (fd_set*) NULL, &zeroTimeout));
 
     // Currently we rebuild the entire interface list whenever any interface change is
     // detected. If this ever proves to be a performance issue in a multi-homed
     // configuration, more care should be paid to changedInterfaces.
-    if (changedInterfaces)
+    if (changedInterfaces.Head != NULL)
         mDNSPlatformPosixRefreshInterfaceList(pChgRec->mDNS);
+
+    while ((changedInterface = (NetworkInterfaceIndex*)changedInterfaces.Head) != NULL)
+    {
+        RemoveFromList(&changedInterfaces, changedInterface);
+        mdns_free(changedInterface);
+    }
 }
 
 // Register with either a Routing Socket or RtNetLink to listen for interface changes.
-- 
2.35.1