iface: refresh hw address when interface appears via netlink

getmac() is only called once during config parsing.  If the interface
does not exist at that point, ifi_hwaddr stays all-zeroes and IGMP
queries are later sent with a source MAC of 00:00:00:00:00:00.

Fix by calling config_iface_update() from iface_add(), so the hardware
address is fetched at the moment the interface actually appears in the
system.

Fixes: #4

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

Author: troglobit

src/config.c

@@ -100,6 +100,17 @@ static int getmac(const char *ifname, uint8_t *mac, size_t size)
     return rc;
 }
 
+/*
+ * Fetch (or re-fetch) the hardware address for an interface.  Called when
+ * an interface appears via netlink to handle the case where the interface
+ * did not exist when the config was first parsed.
+ */
+void config_iface_update(struct ifi *ifi)
+{
+    if (getmac(ifi->ifi_name, ifi->ifi_hwaddr, sizeof(ifi->ifi_hwaddr)))
+	warn("failed finding hw address for iface %s", ifi->ifi_name);
+}
+
 /*
  * Called by parser to add an interface to start or watch for in the future
  */

src/defs.h

@@ -159,6 +159,7 @@ extern struct ifi      *config_find_ifname(char *);
 extern struct ifi      *config_find_ifaddr(in_addr_t);
 extern struct ifi      *config_find_iface(int, int);
 extern struct ifi      *config_init_tunnel(in_addr_t, in_addr_t, uint32_t);
+extern void             config_iface_update(struct ifi *);
 extern void             config_iface_addr_add(int, struct sockaddr *, unsigned int);
 extern void		config_iface_init(void);
 

src/iface.c

@@ -193,6 +193,7 @@ void iface_add(int ifindex, int flags)
 
     dbg("Marking %s as now available in system", ifi->ifi_name);
     ifi->ifi_index = ifindex;
+    config_iface_update(ifi);
 
     iface_check(ifindex, flags);
 }