From: Roy Marples <roy@marples.name>
Date: Fri, 26 Feb 2010 20:37:30 +0000 (+0000)
Subject: Enable net.ipv4.conf.$iface.promote_secondaries on Linux so that
X-Git-Tag: v5.2.0~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=255e14dab144a3f6cb1910d9ea164afa9ff98220;p=thirdparty%2Fdhcpcd.git

Enable net.ipv4.conf.$iface.promote_secondaries on Linux so that
we keep the subnet when changing addresses on the same subnet.
---

diff --git a/if-bsd.c b/if-bsd.c
index 58c405f8..05a2d515 100644
--- a/if-bsd.c
+++ b/if-bsd.c
@@ -72,6 +72,13 @@
 
 static int r_fd = -1;
 
+int
+if_init(_unused struct interface *iface)
+{
+	/* BSD promotes secondary address by default */
+	return 0;
+}
+
 int
 init_sockets(void)
 {
diff --git a/if-linux.c b/if-linux.c
index d24b956e..705f7753 100644
--- a/if-linux.c
+++ b/if-linux.c
@@ -59,6 +59,32 @@
 static int sock_fd;
 static struct sockaddr_nl sock_nl;
 
+int
+if_init(struct interface *iface)
+{
+	char path[PATH_MAX];
+	FILE *fp;
+	int n;
+
+	/* We enable promote_secondaries so that we can do this
+	 * add 192.168.1.2/24
+	 * add 192.168.1.3/24
+	 * del 192.168.1.2/24
+	 * and the subnet mask moves onto 192.168.1.3/24
+	 * This matches the behaviour of BSD which makes coding dhcpcd
+	 * a little easier as there's just one behaviour. */
+	snprintf(path, sizeof(path),
+	    "/proc/sys/net/ipv4/conf/%s/promote_secondaries",
+	    iface->name);
+
+	fp = fopen(path, "w");
+	if (fp == NULL)
+		return errno == ENOENT ? 0 : -1;
+	n = fprintf(fp, "1");
+	fclose(fp);
+	return n == -1 ? -1 : 0;
+}
+
 static int
 _open_link_socket(struct sockaddr_nl *nl)
 {
diff --git a/net.c b/net.c
index b55a7108..20edd0e7 100644
--- a/net.c
+++ b/net.c
@@ -449,6 +449,14 @@ discover_interfaces(int argc, char * const *argv)
 				    "%s: unknown hardware family", p);
 			}
 		}
+
+		/* Handle any platform init for the interface */
+		if (if_init(ifp) == -1) {
+			syslog(LOG_ERR, "%s: if_init: %m", p);
+			free_interface(ifp);
+			continue;
+		}
+
 		if (ifl)
 			ifl->next = ifp; 
 		else
diff --git a/net.h b/net.h
index d1e9c066..4f92f0a7 100644
--- a/net.h
+++ b/net.h
@@ -105,6 +105,8 @@ int inet_ntocidr(struct in_addr);
 int inet_cidrtoaddr(int, struct in_addr *);
 
 int up_interface(struct interface *);
+int if_init(struct interface *);
+
 int do_address(const char *,
     struct in_addr *, struct in_addr *, struct in_addr *, int);
 int if_address(const struct interface *,
diff --git a/platform-linux.c b/platform-linux.c
index c0bc5994..99cb4a35 100644
--- a/platform-linux.c
+++ b/platform-linux.c
@@ -25,9 +25,6 @@
  * SUCH DAMAGE.
  */
 
-#include <sys/param.h>
-#include <sys/sysctl.h>
-
 #include <errno.h>
 #include <stdio.h>
 #include <string.h>