Add if_nameindex(3).

libc/Makefile

@@ -412,6 +412,10 @@ netdb/getservent.o \
 netdb/setnetent.o \
 netdb/setprotoent.o \
 netdb/setservent.o \
+net/if/if_freenameindex.o \
+net/if/if_indextoname.o \
+net/if/if_nameindex.o \
+net/if/if_nametoindex.o \
 poll/poll.o \
 poll/ppoll.o \
 psctl/psctl.o \

libc/include/net/if.h

@@ -74,4 +74,23 @@ struct if_config
 };
 #endif
 
+struct if_nameindex
+{
+	unsigned int if_index;
+	char* if_name;
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void if_freenameindex(struct if_nameindex*);
+char* if_indextoname(unsigned int, char*);
+struct if_nameindex* if_nameindex(void);
+unsigned int if_nametoindex(const char*);
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
 #endif

libc/net/if/if_freenameindex.c

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2016 Jonas 'Sortie' Termansen.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * net/if/if_freenameindex.c
+ * Free list of network interfaces.
+ */
+
+#include <net/if.h>
+#include <stdlib.h>
+
+void if_freenameindex(struct if_nameindex* ifs)
+{
+	for ( size_t i = 0; ifs[i].if_name; i++ )
+		free(ifs[i].if_name);
+	free(ifs);
+}

libc/net/if/if_indextoname.c

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2016 Jonas 'Sortie' Termansen.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * net/if/if_indextoname.c
+ * Get name of network interface by index.
+ */
+
+#include <errno.h>
+#include <net/if.h>
+#include <stdlib.h>
+#include <string.h>
+
+// TODO: This is better done with a dedicated system call.
+char* if_indextoname(unsigned int ifindex, char* str)
+{
+	struct if_nameindex* ifs = if_nameindex();
+	if ( !ifs )
+		return NULL;
+	for ( size_t i = 0; ifs[i].if_index; i++ )
+	{
+		if ( ifs[i].if_index == ifindex )
+		{
+			strlcpy(str, ifs[i].if_name, IF_NAMESIZE);
+			if_freenameindex(ifs);
+			return str;
+		}
+	}
+	if_freenameindex(ifs);
+	return errno = ENXIO, (char*) NULL;
+}

libc/net/if/if_nameindex.c

@@ -0,0 +1,119 @@
+/*
+ * Copyright (c) 2016, 2017 Jonas 'Sortie' Termansen.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * net/if/if_nameindex.c
+ * Build list of network interfaces.
+ */
+
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <net/if.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+// TODO: Consider turning this into a system call to avoid a number of error
+//       cases and work properly in chroots.
+struct if_nameindex* if_nameindex(void)
+{
+	DIR* dir = opendir("/dev");
+	if ( !dir )
+		return NULL;
+	struct if_nameindex* ifs = (struct if_nameindex*)
+		reallocarray(NULL, sizeof(struct if_nameindex), 2);
+	if ( !ifs )
+		return closedir(dir), (struct if_nameindex*) NULL;
+	size_t ifs_count = 0;
+	size_t ifs_allocated = 2;
+	ifs[ifs_count].if_index = 0;
+	ifs[ifs_count].if_name = NULL;
+	struct dirent* entry;
+	while ( (errno = 0, entry = readdir(dir)) )
+	{
+		if ( entry->d_type != DT_UNKNOWN && entry->d_type != DT_CHR )
+			continue;
+		int fd = openat(dirfd(dir), entry->d_name, O_RDWR | O_NOFOLLOW);
+		if ( fd < 0 )
+		{
+			int errnum = errno;
+			if ( entry->d_type == DT_UNKNOWN )
+			{
+				struct stat st;
+				if ( fstatat(dirfd(dir), entry->d_name, &st,
+				             AT_SYMLINK_NOFOLLOW) < 0 )
+				{
+					closedir(dir);
+					if_freenameindex(ifs);
+					return NULL;
+				}
+				if ( !S_ISCHR(st.st_mode) )
+					continue;
+			}
+			if ( errnum == ELOOP || errnum == EACCES || errnum == EPERM )
+				continue;
+			closedir(dir);
+			if_freenameindex(ifs);
+			return NULL;
+		}
+		int type;
+		struct if_info info;
+		if ( (type = ioctl(fd, IOCGETTYPE)) < 0 ||
+		     IOC_TYPE(type) != IOC_TYPE_NETWORK_INTERFACE ||
+		     ioctl(fd, NIOC_GETINFO, &info) < 0 )
+		{
+			close(fd);
+			continue;
+		}
+		close(fd);
+		if ( ifs_count + 1 == ifs_allocated )
+		{
+			size_t new_allocated = 2 * ifs_allocated;
+			struct if_nameindex* new_ifs = (struct if_nameindex*)
+				reallocarray(ifs, sizeof(struct if_nameindex), new_allocated);
+			if ( !new_ifs )
+			{
+				closedir(dir);
+				if_freenameindex(ifs);
+				return NULL;
+			}
+			ifs = new_ifs;
+			ifs_allocated = new_allocated;
+		}
+		char* name = strdup(entry->d_name);
+		if ( !name )
+		{
+			closedir(dir);
+			if_freenameindex(ifs);
+			return NULL;
+		}
+		ifs[ifs_count].if_index = info.linkid;
+		ifs[ifs_count].if_name = name;
+		ifs_count++;
+		ifs[ifs_count].if_index = 0;
+		ifs[ifs_count].if_name = NULL;
+	}
+	if ( errno )
+	{
+		closedir(dir);
+		if_freenameindex(ifs);
+		return NULL;
+	}
+	closedir(dir);
+	return ifs;
+}

libc/net/if/if_nametoindex.c

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2016 Jonas 'Sortie' Termansen.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * net/if/if_nametoindex.c
+ * Get index of network interface by name.
+ */
+
+#include <errno.h>
+#include <net/if.h>
+#include <stdlib.h>
+#include <string.h>
+
+// TODO: This is better done with a dedicated system call.
+// TODO: Or at least the name can be looked up directly in /dev.
+unsigned int if_nametoindex(const char* name)
+{
+	struct if_nameindex* ifs = if_nameindex();
+	if ( !ifs )
+		return NULL;
+	for ( size_t i = 0; ifs[i].if_index; i++ )
+	{
+		if ( !strcmp(ifs[i].if_name, name) )
+		{
+			unsigned int result = ifs[i].if_index;
+			if_freenameindex(ifs);
+			return result;
+		}
+	}
+	if_freenameindex(ifs);
+	return 0;
+}

share/man/man4/if.4

@@ -330,6 +330,7 @@ temporarily fail with
 .Xr getsockopt 2 ,
 .Xr ioctl 2 ,
 .Xr setsockopt 2 ,
+.Xr if_nameindex 3 ,
 .Xr arp 4 ,
 .Xr ether 4 ,
 .Xr inet 4 ,