dhcp/0014-Fixed-linux-interface-discovery-using-getifaddrs.patch

From bd50ec560d7bec064190e4d430c066e170732c0e Mon Sep 17 00:00:00 2001
From: Marius Tomaschewski <mt@suse.de>
Date: Tue, 27 Nov 2012 17:44:06 +0100
Subject: [PATCH] Fixed linux interface discovery using getifaddrs

Unlike dhcp 3.x, dhcp 4.x scans interfaces from /proc/net/dev,
which provides only true interface names. When the address set
on the interface has a label assigned (linux 2.0 alias interface
compatibility), then the SIOCGIFADDR requires the label / alias
name as argument instead of the interface name to return this
address. When this is the only address assigned to an interface,
dhcp-server is unable to find any address and fails to start.

Changed to use getifaddrs() function, which retrieves all IP
addresses on linux systems and is available since GLIBC 2.3.
---
 common/discover.c | 51 ++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 44 insertions(+), 7 deletions(-)

diff --git a/common/discover.c b/common/discover.c
index 6a0540b..1dcaa02 100644
--- a/common/discover.c
+++ b/common/discover.c
@@ -370,7 +370,7 @@ end_iface_scan(struct iface_conf_list *ifaces) {
 	ifaces->sock = -1;
 }
 
-#elif __linux /* !HAVE_SIOCGLIFCONF */
+#elif __linux && !(defined(__GNUC_PREREQ) && __GNUC_PREREQ(2,3)) /* !HAVE_SIOCGLIFCONF */
 /* 
  * Linux support
  * -------------
@@ -379,6 +379,14 @@ end_iface_scan(struct iface_conf_list *ifaces) {
  * about interfaces, along with selected ioctl() calls.
  *
  * Linux low level access is documented in the netdevice man page.
+ *
+ * Note: Use getifaddrs instead
+ *   Unfortunately this discover discards all interfaces where the
+ *   only address has a label assigned (linux 2.0 alias interface
+ *   compatibility) as the SIOCGIFADDR requires the the alias name
+ *   (eth0:0) in ifr_name to fetch the address and /proc/net/dev
+ *   on linux > 2.0 lists only the interface names (eth0) without
+ *   any aliases.
  */
 
 /* 
@@ -751,11 +759,11 @@ end_iface_scan(struct iface_conf_list *ifaces) {
 #else
 
 /* 
- * BSD support
- * -----------
+ * BSD & Linux support
+ * -------------------
  *
  * FreeBSD, NetBSD, OpenBSD, and OS X all have the getifaddrs() 
- * function.
+ * function. Linux has it since glibc 2.3.
  *
  * The getifaddrs() man page describes the use.
  */
@@ -812,10 +820,39 @@ next_iface(struct iface_info *info, int *err, struct iface_conf_list *ifaces) {
 		*err = 1;
 		return 0;
 	}
-	strcpy(info->name, ifaces->next->ifa_name);
-	memcpy(&info->addr, ifaces->next->ifa_addr, 
-	       ifaces->next->ifa_addr->sa_len);
+	info->addr.ss_family = AF_UNSPEC;
 	info->flags = ifaces->next->ifa_flags;
+#ifdef __linux
+	if (strchr(ifaces->next->ifa_name, ':')) {
+		/*
+		 * the name contains a ':', which may
+		 * be a IPv4 "alias interface" label;
+		 * resolve to the true interface name
+		 */
+		if_indextoname(if_nametoindex(ifaces->next->ifa_name),
+				info->name);
+	} else {
+		strcpy(info->name, ifaces->next->ifa_name);
+	}
+
+	if (ifaces->next->ifa_addr != NULL) {
+		if (ifaces->next->ifa_addr->sa_family == AF_INET) {
+			memcpy(&info->addr, ifaces->next->ifa_addr,
+					sizeof(struct sockaddr_in));
+		} else
+		if (ifaces->next->ifa_addr->sa_family == AF_INET6) {
+			memcpy(&info->addr, ifaces->next->ifa_addr,
+					sizeof(struct sockaddr_in6));
+		}
+		/* else e.g. AF_PACKET / link layer address  */
+	}
+#else
+	strcpy(info->name, ifaces->next->ifa_name);
+	if (ifaces->next->ifa_addr != NULL) {
+		memcpy(&info->addr, ifaces->next->ifa_addr,
+		       ifaces->next->ifa_addr->sa_len);
+	}
+#endif
 	ifaces->next = ifaces->next->ifa_next;
 	*err = 0;
 	return 1;
-- 
1.8.4