Trie: Simplify network matching code

Introduce ipX_prefix_equal() and use it to simplify network matching code.

2 files changed, 84 insertions, 0 deletions

diff --git a/lib/ip.h b/lib/ip.h
index cc36ce64..9eef2e16 100644
--- a/lib/ip.h
+++ b/lib/ip.h
@@ -279,6 +279,24 @@ static inline uint ip6_pxlen(ip6_addr a, ip6_addr b)
   return 32 * i + 31 - u32_log2(a.addr[i] ^ b.addr[i]);
 }
 
+static inline int ip4_prefix_equal(ip4_addr a, ip4_addr b, uint n)
+{
+  return (_I(a) ^ _I(b)) < ((u64) 1 << (32 - n));
+}
+
+static inline int ip6_prefix_equal(ip6_addr a, ip6_addr b, uint n)
+{
+  uint n0 = n / 32;
+  uint n1 = n % 32;
+
+  return
+    ((n0 <= 0) || (_I0(a) == _I0(b))) &&
+    ((n0 <= 1) || (_I1(a) == _I1(b))) &&
+    ((n0 <= 2) || (_I2(a) == _I2(b))) &&
+    ((n0 <= 3) || (_I3(a) == _I3(b))) &&
+    (!n1 || ((a.addr[n0] ^ b.addr[n0]) < (1u << (32 - n1))));
+}
+
 static inline u32 ip4_getbit(ip4_addr a, uint pos)
 { return (_I(a) >> (31 - pos)) & 1; }
 
diff --git a/lib/ip_test.c b/lib/ip_test.c
index 36d10d68..eee0a427 100644
--- a/lib/ip_test.c
+++ b/lib/ip_test.c
@@ -167,6 +167,70 @@ t_ip6_ntop(void)
   return bt_assert_batch(test_vectors, test_ipa_ntop, bt_fmt_ipa, bt_fmt_str);
 }
 
+static int
+t_ip4_prefix_equal(void)
+{
+  bt_assert( ip4_prefix_equal(ip4_from_u32(0x12345678), ip4_from_u32(0x1234ffff), 16));
+  bt_assert(!ip4_prefix_equal(ip4_from_u32(0x12345678), ip4_from_u32(0x1234ffff), 17));
+  bt_assert( ip4_prefix_equal(ip4_from_u32(0x12345678), ip4_from_u32(0x12345000), 21));
+  bt_assert(!ip4_prefix_equal(ip4_from_u32(0x12345678), ip4_from_u32(0x12345000), 22));
+
+  bt_assert( ip4_prefix_equal(ip4_from_u32(0x00000000), ip4_from_u32(0xffffffff),  0));
+  bt_assert( ip4_prefix_equal(ip4_from_u32(0x12345678), ip4_from_u32(0x12345678),  0));
+
+  bt_assert( ip4_prefix_equal(ip4_from_u32(0x12345678), ip4_from_u32(0x12345678),  32));
+  bt_assert(!ip4_prefix_equal(ip4_from_u32(0x12345678), ip4_from_u32(0x12345679),  32));
+  bt_assert(!ip4_prefix_equal(ip4_from_u32(0x12345678), ip4_from_u32(0x92345678),  32));
+
+  return 1;
+}
+
+static int
+t_ip6_prefix_equal(void)
+{
+  bt_assert( ip6_prefix_equal(ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20202020),
+			      ip6_build(0x20010db8, 0x1234ffff, 0xfefefefe, 0xdcdcdcdc),
+			      48));
+
+  bt_assert(!ip6_prefix_equal(ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20202020),
+			      ip6_build(0x20010db8, 0x1234ffff, 0xfefefefe, 0xdcdcdcdc),
+			      49));
+
+  bt_assert(!ip6_prefix_equal(ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20202020),
+			      ip6_build(0x20020db8, 0x12345678, 0xfefefefe, 0xdcdcdcdc),
+			      48));
+
+  bt_assert( ip6_prefix_equal(ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20202020),
+			      ip6_build(0x20010db8, 0x12345678, 0xfefefefe, 0xdcdcdcdc),
+			      64));
+
+  bt_assert(!ip6_prefix_equal(ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20202020),
+			      ip6_build(0x20010db8, 0x1234567e, 0xfefefefe, 0xdcdcdcdc),
+			      64));
+
+  bt_assert( ip6_prefix_equal(ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20002020),
+			      ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20202020),
+			      106));
+
+  bt_assert(!ip6_prefix_equal(ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20002020),
+			      ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20202020),
+			      107));
+
+  bt_assert( ip6_prefix_equal(ip6_build(0xfeef0db8, 0x87654321, 0x10101010, 0x20202020),
+			      ip6_build(0x20010db8, 0x12345678, 0xfefefefe, 0xdcdcdcdc),
+			      0));
+
+  bt_assert( ip6_prefix_equal(ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20202020),
+			      ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20202020),
+			      128));
+
+  bt_assert(!ip6_prefix_equal(ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20202020),
+			      ip6_build(0x20010db8, 0x12345678, 0x10101010, 0x20202021),
+			      128));
+
+  return 1;
+}
+
 int
 main(int argc, char *argv[])
 {
@@ -176,6 +240,8 @@ main(int argc, char *argv[])
   bt_test_suite(t_ip6_pton, "Converting IPv6 string to ip6_addr struct");
   bt_test_suite(t_ip4_ntop, "Converting ip4_addr struct to IPv4 string");
   bt_test_suite(t_ip6_ntop, "Converting ip6_addr struct to IPv6 string");
+  bt_test_suite(t_ip4_prefix_equal, "Testing ip4_prefix_equal()");
+  bt_test_suite(t_ip6_prefix_equal, "Testing ip6_prefix_equal()");
 
   return bt_exit_value();
 }