Implement if_nameindex(3)/if_freenameindex(3).
This is just a subset of the recently-implemented getifaddrs(3), though if
we want to handle interfaces (such as "rmnet_*") that don't have an address,
we need to either expose ifaddrs_storage and keep track of which interfaces
we've already seen (which is pretty messy), or refactor the netlink code so
we can reuse it and just extract the information we need for if_nameindex(3).
This patch goes the latter route.
Also clean up if_nametoindex(3) and if_indextoname(3).
Change-Id: I5ffc5df0bab62286cdda2e7af06f032c767119a8
diff --git a/libc/bionic/net_if.cpp b/libc/bionic/net_if.cpp
new file mode 100644
index 0000000..a6b896e
--- /dev/null
+++ b/libc/bionic/net_if.cpp
@@ -0,0 +1,161 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <net/if.h>
+
+#include <errno.h>
+#include <ifaddrs.h>
+#include <linux/if_packet.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <linux/sockios.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "private/ErrnoRestorer.h"
+
+#include "bionic_netlink.h"
+
+char* if_indextoname(unsigned ifindex, char* ifname) {
+ int s = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC, 0);
+ if (s == -1) return nullptr;
+
+ struct ifreq ifr = {};
+ ifr.ifr_ifindex = ifindex;
+
+ int rc = ioctl(s, SIOCGIFNAME, &ifr);
+ ErrnoRestorer errno_restorer;
+ close(s);
+ return (rc == -1) ? nullptr : strncpy(ifname, ifr.ifr_name, IFNAMSIZ);
+}
+
+unsigned if_nametoindex(const char* ifname) {
+ int s = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC, 0);
+ if (s == -1) return 0;
+
+ struct ifreq ifr = {};
+ strncpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
+ ifr.ifr_name[IFNAMSIZ - 1] = 0;
+
+ int rc = ioctl(s, SIOCGIFINDEX, &ifr);
+ ErrnoRestorer errno_restorer;
+ close(s);
+ return (rc == -1) ? 0 : ifr.ifr_ifindex;
+}
+
+struct if_list {
+ if_list* next;
+ struct if_nameindex data;
+
+ if_list(if_list** list) {
+ // push_front onto `list`.
+ next = *list;
+ *list = this;
+ }
+
+ static void Free(if_list* list, bool names_too) {
+ while (list) {
+ if_list* it = list;
+ list = it->next;
+ if (names_too) free(it->data.if_name);
+ free(it);
+ }
+ }
+};
+
+static void __if_nameindex_callback(void* context, nlmsghdr* hdr) {
+ if_list** list = reinterpret_cast<if_list**>(context);
+ if (hdr->nlmsg_type == RTM_NEWLINK) {
+ ifinfomsg* ifi = reinterpret_cast<ifinfomsg*>(NLMSG_DATA(hdr));
+
+ // Create a new entry and set the interface index.
+ if_list* new_link = new if_list(list);
+ new_link->data.if_index = ifi->ifi_index;
+
+ // Go through the various bits of information and find the name.
+ rtattr* rta = IFLA_RTA(ifi);
+ size_t rta_len = IFLA_PAYLOAD(hdr);
+ while (RTA_OK(rta, rta_len)) {
+ if (rta->rta_type == IFLA_IFNAME) {
+ new_link->data.if_name = strndup(reinterpret_cast<char*>(RTA_DATA(rta)), RTA_PAYLOAD(rta));
+ }
+ rta = RTA_NEXT(rta, rta_len);
+ }
+ }
+}
+
+struct if_nameindex* if_nameindex() {
+ if_list* list = nullptr;
+
+ // Open the netlink socket and ask for all the links;
+ NetlinkConnection nc;
+ bool okay = nc.SendRequest(RTM_GETLINK) && nc.ReadResponses(__if_nameindex_callback, &list);
+ if (!okay) {
+ if_list::Free(list, true);
+ return nullptr;
+ }
+
+ // Count the interfaces.
+ size_t interface_count = 0;
+ for (if_list* it = list; it != nullptr; it = it->next) {
+ ++interface_count;
+ }
+
+ // Build the array POSIX requires us to return.
+ struct if_nameindex* result = new struct if_nameindex[interface_count + 1];
+ if (result) {
+ struct if_nameindex* out = result;
+ for (if_list* it = list; it != nullptr; it = it->next) {
+ out->if_index = it->data.if_index;
+ out->if_name = it->data.if_name;
+ ++out;
+ }
+ out->if_index = 0;
+ out->if_name = nullptr;
+ }
+
+ // Free temporary storage.
+ if_list::Free(list, false);
+
+ return result;
+}
+
+void if_freenameindex(struct if_nameindex* array) {
+ if (array == nullptr) return;
+
+ struct if_nameindex* ptr = array;
+ while (ptr->if_index != 0 || ptr->if_name != nullptr) {
+ free(ptr->if_name);
+ ++ptr;
+ }
+
+ delete[] array;
+}