This function computes the number of common octets between two IPv6 addresses,
for use in Babel prefix compression.
Signed-off-by: Toke Høiland-Jørgensen <t...@toke.dk>
---
lib/ip.c | 14 ++++++++++++++
lib/ip.h | 1 +
2 files changed, 15 insertions(+)
diff --git a/lib/ip.c b/lib/ip.c
index 9497248c..af81704b 100644
--- a/lib/ip.c
+++ b/lib/ip.c
@@ -33,6 +33,20 @@ ip6_compare(ip6_addr a, ip6_addr b)
return 0;
}
+int
+ip6_common_octets(ip6_addr a, ip6_addr b)
+{
+ int i, j, common = 0;
+ for (i=0; i<4; i++)
+ for (j=3; j>=0; j--)
+ if ((0xff & (a.addr[i] >> (8*j))) == (0xff & (b.addr[i] >> (8*j))))
+ common++;
+ else
+ return common;
+
+ return common;
+}
+
ip6_addr
ip6_mkmask(uint n)
{
diff --git a/lib/ip.h b/lib/ip.h
index 5cfce1f1..b4909984 100644
--- a/lib/ip.h
+++ b/lib/ip.h
@@ -205,6 +205,7 @@ static inline int ip4_compare(ip4_addr a, ip4_addr b)
{ return (_I(a) > _I(b)) - (_I(a) < _I(b)); }
int ip6_compare(ip6_addr a, ip6_addr b);
+int ip6_common_octets(ip6_addr a, ip6_addr b);
#define ipa_hash(x) ip6_hash(x)
#define ipa_compare(x,y) ip6_compare(x,y)
--
2.13.0
