Trie: Simplify network matching code

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

filter/trie.c

@@ -424,9 +424,6 @@ trie_add_prefix(struct f_trie *t, const net_addr *net, uint l, uint h)
 static int
 trie_match_net4(const struct f_trie *t, ip4_addr px, uint plen)
 {
-  ip4_addr pmask = ip4_mkmask(plen);
-  ip4_addr paddr = ip4_and(px, pmask);
-
   if (plen == 0)
     return t->zero;
 
@@ -437,10 +434,8 @@ trie_match_net4(const struct f_trie *t, ip4_addr px, uint plen)
 
   while (n)
   {
-    ip4_addr cmask = ip4_and(n->mask, pmask);
-
     /* We are out of path */
-    if (ip4_compare(ip4_and(paddr, cmask), ip4_and(n->addr, cmask)))
+    if (!ip4_prefix_equal(px, n->addr, MIN(plen, n->plen)))
       return 0;
 
     /* Check local mask */
@@ -452,11 +447,11 @@ trie_match_net4(const struct f_trie *t, ip4_addr px, uint plen)
       return 1;
 
     /* We finished trie walk and still no match */
-    if (plen <= n->plen)
+    if (nlen <= n->plen)
       return 0;
 
     /* Choose children */
-    n =  n->c[ip4_getbits(paddr, n->plen, TRIE_STEP)];
+    n =  n->c[ip4_getbits(px, n->plen, TRIE_STEP)];
   }
 
   return 0;
@@ -465,9 +460,6 @@ trie_match_net4(const struct f_trie *t, ip4_addr px, uint plen)
 static int
 trie_match_net6(const struct f_trie *t, ip6_addr px, uint plen)
 {
-  ip6_addr pmask = ip6_mkmask(plen);
-  ip6_addr paddr = ip6_and(px, pmask);
-
   if (plen == 0)
     return t->zero;
 
@@ -478,10 +470,8 @@ trie_match_net6(const struct f_trie *t, ip6_addr px, uint plen)
 
   while (n)
   {
-    ip6_addr cmask = ip6_and(n->mask, pmask);
-
     /* We are out of path */
-    if (ip6_compare(ip6_and(paddr, cmask), ip6_and(n->addr, cmask)))
+    if (!ip6_prefix_equal(px, n->addr, MIN(plen, n->plen)))
       return 0;
 
     /* Check local mask */
@@ -493,11 +483,11 @@ trie_match_net6(const struct f_trie *t, ip6_addr px, uint plen)
       return 1;
 
     /* We finished trie walk and still no match */
-    if (plen <= n->plen)
+    if (nlen <= n->plen)
       return 0;
 
     /* Choose children */
-    n =  n->c[ip6_getbits(paddr, n->plen, TRIE_STEP)];
+    n =  n->c[ip6_getbits(px, n->plen, TRIE_STEP)];
   }
 
   return 0;

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; }
 

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();
 }