From 70473a5f8c56d8ec2e837b9b66443dc252b24da9 Mon Sep 17 00:00:00 2001
From: Thierry Fournier <tfournier@arpalert.org>
Date: Wed, 17 Feb 2016 17:12:14 +0100
Subject: [PATCH] MINOR: common: mask conversion

Add function which converts network mask from bit length form
to struct in*_addr form.
---
 include/common/standard.h | 10 ++++++++++
 src/standard.c            | 31 +++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/include/common/standard.h b/include/common/standard.h
index a66317171..9abdb0643 100644
--- a/include/common/standard.h
+++ b/include/common/standard.h
@@ -832,6 +832,16 @@ static inline int set_host_port(struct sockaddr_storage *addr, int port)
 	return 0;
 }
 
+/* Convert mask from bit length form to in_addr form.
+ * This function never fails.
+ */
+void len2mask4(int len, struct in_addr *addr);
+
+/* Convert mask from bit length form to in6_addr form.
+ * This function never fails.
+ */
+void len2mask6(int len, struct in6_addr *addr);
+
 /* Return true if IPv4 address is part of the network */
 extern int in_net_ipv4(struct in_addr *addr, struct in_addr *mask, struct in_addr *net);
 
diff --git a/src/standard.c b/src/standard.c
index f4da01bc2..30883d759 100644
--- a/src/standard.c
+++ b/src/standard.c
@@ -1002,6 +1002,37 @@ int cidr2dotted(int cidr, struct in_addr *mask) {
 	return 1;
 }
 
+/* Convert mask from bit length form to in_addr form.
+ * This function never fails.
+ */
+void len2mask4(int len, struct in_addr *addr)
+{
+	if (len >= 32) {
+		addr->s_addr = 0xffffffff;
+		return;
+	}
+	if (len <= 0) {
+		addr->s_addr = 0x00000000;
+		return;
+	}
+	addr->s_addr = 0xffffffff << (32 - len);
+	addr->s_addr = htonl(addr->s_addr);
+}
+
+/* Convert mask from bit length form to in6_addr form.
+ * This function never fails.
+ */
+void len2mask6(int len, struct in6_addr *addr)
+{
+	len2mask4(len, (struct in_addr *)&addr->s6_addr[0]); /* msb */
+	len -= 32;
+	len2mask4(len, (struct in_addr *)&addr->s6_addr[4]);
+	len -= 32;
+	len2mask4(len, (struct in_addr *)&addr->s6_addr[8]);
+	len -= 32;
+	len2mask4(len, (struct in_addr *)&addr->s6_addr[12]); /* lsb */
+}
+
 /*
  * converts <str> to two struct in_addr* which must be pre-allocated.
  * The format is "addr[/mask]", where "addr" cannot be empty, and mask