[IPV4]: All deletion of equal addresses only differing by prefix length.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 33 insertions, 0 deletions

diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index 6fafb27877a7..e04b71cd9e73 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -7,6 +7,7 @@
 #include <linux/netdevice.h>
 #include <linux/rcupdate.h>
 #include <linux/timer.h>
+#include <linux/rtnetlink.h>
 
 struct ipv4_devconf
 {
@@ -131,6 +132,25 @@ static __inline__ int bad_mask(u32 mask, u32 addr)
 	return 0;
 }
 
+static inline int inet_ifa_match_local_prefixlen(struct ifaddrmsg *ifm,
+						 struct in_ifaddr *ifa)
+{
+	int real_prefixlen = IFA_REAL_DEL_PREFIX(ifm->ifa_prefixlen);
+
+	/*
+	 * Since the prefix length hasn't been taken into account in
+	 * previous kernel versions, parts of the userspace rely on the fact
+	 * that the deletion of an address without specifying a prefix works.
+	 * We cannot break this and thus a prefix length of 32 still represents
+	 * a wildcard if no exact match is requested.
+	 */
+	if (real_prefixlen != 32 || ifm->ifa_prefixlen & IFA_PREFIX_EXACT_DEL)
+		if (real_prefixlen != ifa->ifa_prefixlen)
+			return 0;
+
+	return 1;
+}
+
 #define for_primary_ifa(in_dev)	{ struct in_ifaddr *ifa; \
   for (ifa = (in_dev)->ifa_list; ifa && !(ifa->ifa_flags&IFA_F_SECONDARY); ifa = ifa->ifa_next)
 
diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index dbfe0df7795f..b3fec31e7e6f 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -397,6 +397,19 @@ enum
 
 #define IFA_MAX (__IFA_MAX - 1)
 
+/*
+ * Quirk for IPv4 address deletion to allow exact deletion of equal
+ * addresses varying only in prefix length. A explicit exact comparison
+ * of the prefix length will only be done if IFA_PREFIX_EXACT_DEL is
+ * ORed to ifa_prefixlen.
+ *
+ * Note: This special treatment is only understood while deleting
+ *       addresses and will lead to unexpected behaviour if used
+ *       otherwise.
+ */
+#define IFA_PREFIX_EXACT_DEL	0x40
+#define IFA_REAL_DEL_PREFIX(l)	((l) & 0x3f)
+
 /* ifa_flags */
 
 #define IFA_F_SECONDARY		0x01