Add the exact matching modifier support "=" to the NCCL_IB_HCA variable (#236)

Perform exact matching when the prefix "=" is specified in the NCCL_IB_HCA variable to exclude HCAs mlx5_X[0-9]+ when mlx5_X is specified.

src/include/socket.h

@@ -66,6 +66,7 @@ static int findInterfaces(const char* prefixList, char* names, union socketAddre
 #endif
   struct netIf userIfs[MAX_IFS];
   bool searchNot = prefixList && prefixList[0] == '^';
+  bool searchExact = prefixList && prefixList[0] == '=';
   int nUserIfs = parseStringList(prefixList, userIfs, MAX_IFS);
 
   int found = 0;
@@ -92,7 +93,7 @@ static int findInterfaces(const char* prefixList, char* names, union socketAddre
     }
 
     // check against user specified interfaces
-    if (!(matchIfList(interface->ifa_name, -1, userIfs, nUserIfs) ^ searchNot)) {
+    if (!(matchIfList(interface->ifa_name, -1, userIfs, nUserIfs, searchExact) ^ searchNot)) {
       continue;
     }
 

src/include/utils.h

@@ -20,6 +20,6 @@ struct netIf {
 };
 
 int parseStringList(const char* string, struct netIf* ifList, int maxList);
-bool matchIfList(const char* string, int port, struct netIf* ifList, int listSize);
+bool matchIfList(const char* string, int port, struct netIf* ifList, int listSize, bool matchExact);
 
 #endif