LibC: Implement if_indextoname and if_nametoindex

Userland/Libraries/LibC/net.cpp

@@ -7,20 +7,54 @@
 #include <errno.h>
 #include <net/if.h>
 #include <netinet/in.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
 
 const in6_addr in6addr_any = IN6ADDR_ANY_INIT;
 const in6_addr in6addr_loopback = IN6ADDR_LOOPBACK_INIT;
 
+// https://pubs.opengroup.org/onlinepubs/9699919799/functions/if_nametoindex.html
 unsigned int if_nametoindex([[maybe_unused]] char const* ifname)
 {
-    errno = ENODEV;
-    return -1;
+    int dummy_socket = socket(AF_INET, SOCK_DGRAM, 0);
+    if (dummy_socket < 0) {
+        errno = -dummy_socket;
+        return 0;
+    }
+
+    struct ifreq ifr;
+    memcpy(ifr.ifr_name, ifname, IF_NAMESIZE);
+
+    int rc = ioctl(dummy_socket, SIOCGIFINDEX, &ifr);
+    if (rc) {
+        errno = -rc;
+        return 0;
+    }
+
+    return ifr.ifr_index;
 }
 
+// https://pubs.opengroup.org/onlinepubs/9699919799/functions/if_indextoname.html#tag_16_236
 char* if_indextoname([[maybe_unused]] unsigned int ifindex, [[maybe_unused]] char* ifname)
 {
-    errno = ENXIO;
-    return nullptr;
+    int dummy_socket = socket(AF_INET, SOCK_DGRAM, 0);
+    if (dummy_socket < 0) {
+        errno = -dummy_socket;
+        return 0;
+    }
+
+    struct ifreq ifr;
+    ifr.ifr_index = ifindex;
+
+    int rc = ioctl(dummy_socket, SIOCGIFNAME, &ifr);
+    if (rc) {
+        errno = -rc;
+        return nullptr;
+    }
+
+    memcpy(ifname, ifr.ifr_name, IF_NAMESIZE);
+    return ifname;
 }
 
 // https://pubs.opengroup.org/onlinepubs/9699919799/functions/if_nameindex.html