support the special interface name _first_ for ethernet/wireless

Since we have deterministic device names in Linux, these strings are a
much better default in the i3status config than "eth0" and "wlan0" (what
we used before).

1 files changed, 39 insertions, 0 deletions

diff --git a/src/first_network_device.c b/src/first_network_device.c
new file mode 100644
index 0000000..c160027
--- /dev/null
+++ b/src/first_network_device.c
@@ -0,0 +1,39 @@
+// vim:ts=8:expandtab
+#include <sys/stat.h>
+#include <stdlib.h>
+#include <ifaddrs.h>
+
+#include "i3status.h"
+
+const char *first_eth_interface(const net_type_t type) {
+        static char *interface = NULL;
+        struct ifaddrs *ifaddr, *addrp;
+        struct stat stbuf;
+        static char path[1024];
+
+        getifaddrs(&ifaddr);
+
+        if (ifaddr == NULL)
+                return NULL;
+
+        free(interface);
+        interface = NULL;
+        for (addrp = ifaddr;
+             addrp != NULL;
+             addrp = addrp->ifa_next) {
+                if (strncasecmp("lo", addrp->ifa_name, strlen("lo")) == 0)
+                        continue;
+                // Skip this interface if it is a wireless interface.
+                snprintf(path, sizeof(path), "/sys/class/net/%s/wireless", addrp->ifa_name);
+                const bool is_wireless = (stat(path, &stbuf) == 0);
+                if (( is_wireless && type == NET_TYPE_ETHERNET) ||
+                    (!is_wireless && type == NET_TYPE_WIRELESS))
+                        continue;
+                interface = strdup(addrp->ifa_name);
+                break;
+        }
+
+        freeifaddrs(ifaddr);
+        return interface;
+}
+