Implement getifaddrs()

include/ifaddrs.h

@@ -0,0 +1,73 @@
+/* ifaddrs.h -- declarations for getting network interface addresses
+   Copyright (C) 2002-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _IFADDRS_H
+#define _IFADDRS_H	1
+
+#include <features.h>
+#include <sys/socket.h>
+
+__BEGIN_DECLS
+
+/* The `getifaddrs' function generates a linked list of these structures.
+   Each element of the list describes one network interface.  */
+struct ifaddrs
+{
+  struct ifaddrs *ifa_next;	/* Pointer to the next structure.  */
+
+  char *ifa_name;		/* Name of this network interface.  */
+  unsigned int ifa_flags;	/* Flags as from SIOCGIFFLAGS ioctl.  */
+
+  struct sockaddr *ifa_addr;	/* Network address of this interface.  */
+  struct sockaddr *ifa_netmask; /* Netmask of this interface.  */
+  union
+  {
+    /* At most one of the following two is valid.  If the IFF_BROADCAST
+       bit is set in `ifa_flags', then `ifa_broadaddr' is valid.  If the
+       IFF_POINTOPOINT bit is set, then `ifa_dstaddr' is valid.
+       It is never the case that both these bits are set at once.  */
+    struct sockaddr *ifu_broadaddr; /* Broadcast address of this interface. */
+    struct sockaddr *ifu_dstaddr; /* Point-to-point destination address.  */
+  } ifa_ifu;
+  /* These very same macros are defined by <net/if.h> for `struct ifaddr'.
+     So if they are defined already, the existing definitions will be fine.  */
+# ifndef ifa_broadaddr
+#  define ifa_broadaddr	ifa_ifu.ifu_broadaddr
+# endif
+# ifndef ifa_dstaddr
+#  define ifa_dstaddr	ifa_ifu.ifu_dstaddr
+# endif
+
+  void *ifa_data;		/* Address-specific data (may be unused).  */
+};
+
+
+/* Create a linked list of `struct ifaddrs' structures, one for each
+   network interface on the host machine.  If successful, store the
+   list in *IFAP and return 0.  On errors, return -1 and set `errno'.
+
+   The storage returned in *IFAP is allocated dynamically and can
+   only be properly freed by passing it to `freeifaddrs'.  */
+extern int getifaddrs (struct ifaddrs **__ifap) __THROW;
+
+/* Reclaim the storage allocated by a previous `getifaddrs' call.  */
+extern void freeifaddrs (struct ifaddrs *__ifa)  __THROW;
+
+__END_DECLS
+
+#endif /* ifaddrs.h */

socket/SRCFILES

@@ -65,4 +65,5 @@ SRCFILES = \
 	socket.c \
 	socketpair.c \
 	sockets_global.c \
-	writev.c
+	writev.c \
+	ifaddrs.c

socket/ifaddrs.c

@@ -0,0 +1,180 @@
+/* getifaddrs -- get names and addresses of all network interfaces
+   Copyright (C) 2002-2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <ifaddrs.h>
+#include <net/if.h>
+#include <sys/socket.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <netinet/in.h>
+
+#define ISLOOPBACK(p) ((p)->ifr_flags & IFF_LOOPBACK)
+
+__typeof__(getifaddrs) __getifaddrs;
+
+
+/* Create a linked list of `struct ifaddrs' structures, one for each
+   network interface on the host machine.  If successful, store the
+   list in *IFAP and return 0.  On errors, return -1 and set `errno'.  */
+int __getifaddrs(struct ifaddrs **ifap)
+{
+	/* This implementation handles only IPv4 interfaces.
+	   The various ioctls below will only work on an AF_INET socket.
+	   Some different mechanism entirely must be used for IPv6.  */
+	int fd;
+	struct ifconf ifc;
+	struct ifreq *ifr;
+	struct ifreq *ibuf;
+	struct ifaddrs **last;
+	struct {
+		struct ifaddrs ia;
+		struct sockaddr addr;
+		struct sockaddr netmask;
+		struct sockaddr broadaddr;
+	} *storage;
+	int i, nifs;
+	size_t namelen;
+	char *names;
+
+	*ifap = NULL;
+	fd = socket(AF_INET, SOCK_DGRAM, 0);
+	if (fd < 0)
+		return -1;
+
+	ifc.ifc_len = 0;
+	ifc.ifc_buf = NULL;
+ 	if (ioctl(fd, SIOCGIFCONF, (char *)&ifc) < 0 ||
+	    ifc.ifc_len < (int)sizeof(struct ifreq))
+	{
+		close(fd);
+		return -1;
+	}
+	nifs = (int)(ifc.ifc_len / sizeof(struct ifreq));
+	ibuf = malloc(nifs * sizeof(*ibuf));
+	if (ibuf == NULL)
+	{
+		close(fd);
+		return -1;
+	}
+	ifc.ifc_len = nifs * sizeof(*ibuf);
+	ifc.ifc_buf = (void *)ibuf;
+
+ 	if (ioctl(fd, SIOCGIFCONF, (char *)&ifc) < 0 ||
+	    ifc.ifc_len < (int)sizeof(struct ifreq))
+	{
+		free(ibuf);
+		close(fd);
+		return -1;
+	}
+	nifs = (int)(ifc.ifc_len / sizeof(struct ifreq));
+
+	namelen = 0;
+	for (i = 0; i < nifs; i++)
+		namelen += strlen(ibuf[i].ifr_name) + 1;
+
+	storage = malloc((nifs * sizeof(*storage)) + namelen);
+	if (storage == NULL)
+	{
+		free(ibuf);
+		close(fd);
+		return -1;
+	}
+	names = (char *)(storage + nifs);
+
+	/* Now get the list of interfaces and each one's address.
+	   Put it into the expected format and fill in the remaining details.  */
+	last = ifap;
+	for (i = 0; i < nifs; i++, storage++)
+	{
+		ifr = &ibuf[i];
+		storage->ia.ifa_next = NULL;
+		*last = &storage->ia;
+		last = &(storage->ia.ifa_next);
+
+		/* Now copy the information we already have from SIOCGIFCONF.  */
+		storage->ia.ifa_name = names;
+		strcpy(names, ifr->ifr_name);
+		names += strlen(names);
+		storage->addr = ifr->ifr_addr;
+		storage->ia.ifa_addr = &storage->addr;
+
+		/* The SIOCGIFCONF call filled in only the name and address.
+		   Now we must also ask for the other information we need.  */
+
+		if (ioctl(fd, SIOCGIFFLAGS, ifr) < 0)
+			break;
+		storage->ia.ifa_flags = ifr->ifr_flags;
+
+		ifr->ifr_addr = storage->addr;
+
+		if (ioctl(fd, SIOCGIFNETMASK, ifr) < 0)
+		{
+			storage->ia.ifa_netmask = NULL;
+		} else
+		{
+			storage->ia.ifa_netmask = &storage->netmask;
+			storage->netmask = ifr->ifr_netmask;
+		}
+
+		storage->ia.ifa_broadaddr = NULL;
+		if (ifr->ifr_flags & IFF_BROADCAST)
+		{
+			ifr->ifr_addr = storage->addr;
+			if (ioctl(fd, SIOCGIFBRDADDR, ifr) >= 0)
+			{
+				storage->ia.ifa_broadaddr = &storage->broadaddr;
+				storage->broadaddr = ifr->ifr_broadaddr;
+			}
+		} else if (ifr->ifr_flags & IFF_POINTOPOINT)
+		{
+			ifr->ifr_addr = storage->addr;
+			if (ioctl(fd, SIOCGIFDSTADDR, ifr) >= 0)
+			{
+				storage->ia.ifa_broadaddr = &storage->broadaddr;
+				storage->broadaddr = ifr->ifr_dstaddr;
+			}
+		}
+		storage[i].ia.ifa_data = NULL;	/* Nothing here for now.  */
+	}
+	free(ibuf);
+	close(fd);
+
+	if (i < nifs)					/* Broke out early on error.  */
+	{
+		freeifaddrs(*ifap);
+		*ifap = NULL;
+		return -1;
+	}
+
+	return 0;
+}
+
+weak_alias(__getifaddrs, getifaddrs)
+
+
+__typeof__(freeifaddrs) __freeifaddrs;
+
+void freeifaddrs(struct ifaddrs *ifa)
+{
+	free(ifa);
+}
+
+weak_alias(__freeifaddrs, freeifaddrs)