CURLOPT_INTERFACE: avoid resolving interfaces names

Do not try to resolve interfaces names via DNS by recognizing interface
names in a few ways.  If the interface option argument has a prefix of
"if!" then treat the argument as only an interface.  Similarly, if the
interface argument is the name of an interface (even if it does not have
an IP address assigned), treat it as an interface name.  Finally, if the
interface argument is prefixed by "host!" treat it as a hostname that
must be resolved by /etc/hosts or DNS.

These changes allow a client using the multi interfaces to avoid
blocking on name resolution if the interface loses its IP address or
disappears.

1 files changed, 31 insertions, 0 deletions

diff --git a/lib/if2ip.c b/lib/if2ip.c
index 4924f7301..0ae375b15 100644
--- a/lib/if2ip.c
+++ b/lib/if2ip.c
@@ -71,6 +71,24 @@
 
 #if defined(HAVE_GETIFADDRS)
 
+bool Curl_if_is_interface_name(const char *interface)
+{
+  bool result = FALSE;
+
+  struct ifaddrs *iface, *head;
+
+  if(getifaddrs(&head) >= 0) {
+    for(iface=head; iface != NULL; iface=iface->ifa_next) {
+      if(curl_strequal(iface->ifa_name, interface)) {
+        result = TRUE;
+        break;
+      }
+    }
+    freeifaddrs(head);
+  }
+  return result;
+}
+
 char *Curl_if2ip(int af, const char *interface, char *buf, int buf_size)
 {
   struct ifaddrs *iface, *head;
@@ -109,6 +127,14 @@ char *Curl_if2ip(int af, const char *interface, char *buf, int buf_size)
 
 #elif defined(HAVE_IOCTL_SIOCGIFADDR)
 
+bool Curl_if_is_interface_name(const char *interface)
+{
+  /* This is here just to support the old interfaces */
+  char buf[256];
+
+  return (Curl_if2ip(AF_INET, interface, buf, sizeof(buf)) != NULL);
+}
+
 char *Curl_if2ip(int af, const char *interface, char *buf, int buf_size)
 {
   struct ifreq req;
@@ -148,6 +174,11 @@ char *Curl_if2ip(int af, const char *interface, char *buf, int buf_size)
 
 #else
 
+bool Curl_if_is_interface_name(const char *interface)
+{
+  return FALSE;
+}
+
 char *Curl_if2ip(int af, const char *interf, char *buf, int buf_size)
 {
     (void) af;