Partially implement sorting

diff --git a/README.md b/README.md
index 5f6e917d0f9115450f4ee311f1a12b217788dda1..9ed1c187174ece2125df9b5d5cf5c742b261988d 100644 (file)
--- a/README.md
+++ b/README.md
@@ -6,9 +6,9 @@ to an XDP program. It currently supports the entire flowspec match grammar, rate
 action packet match counting (sample bit) and terminal bit, and traffic marking. The redirect
 community is not supported.
 
-Note that correctly sorting rules is *not* implemented as it requires implementing the flowspec
-wire serialization format and it may better be done inside bird/birdc. Thus, be vary careful using
-the terminal bit in the traffict action community.
+Note that correctly sorting rules is *not* fully implemented as it requires implementing the
+flowspec wire serialization format and it may better be done inside bird/birdc. Thus, be vary
+careful using the terminal bit in the traffict action community.
 
 In addition to the communities specified in RFC 8955, two additional communities are supported which
 provide rate-limiting on a per-source basis. When the upper two bytes in an extended community are

diff --git a/genrules.py b/genrules.py
index 3865b6b69f42edf1cab46786213bc380d8196df8..a9f3d16db50c54ee04830757a4d5482fd8d7f39c 100755 (executable)
--- a/genrules.py
+++ b/genrules.py
@@ -12,6 +12,10 @@ IP_PROTO_ICMPV6 = 58
 IP_PROTO_TCP = 6
 IP_PROTO_UDP = 17
 
+ORD_LESS = 0
+ORD_GREATER = 1
+ORD_EQUAL = 2
+
 class ASTAction(Enum):
     OR = 1
     AND = 2
@@ -175,28 +179,67 @@ def parse_bit_expr(expr):
     return ASTNode(ASTAction.EXPR, BitExpr(expr))
 
 
+class IpRule:
+    def __init__(self, ty, offset, net, proto):
+        self.ty = ty
+        self.offset = offset
+        if offset is None:
+            self.offset = 0
+        self.net = net
+        self.proto = proto
+
+    def ord(self, other):
+        assert self.ty == other.ty
+        assert self.proto == other.proto
+        if self.offset < other.offset:
+            return ORD_LESS
+        if self.offset > other.offset:
+            return ORD_GREATER
+
+        if self.net.overlaps(other.net):
+            if self.net.prefixlen > other.net.prefixlen:
+                return ORD_LESS
+            elif self.net.prefixlen < other.net.prefixlen:
+                return ORD_GREATER
+        else:
+            if self.net < other.net:
+                return ORD_LESS
+            else:
+                assert self.net > other.net
+                return ORD_GREATER
+
+        return ORD_EQUAL
+
+    def __lt__(self, other):
+        return self.ord(other) == ORD_LESS
+
+    def __eq__(self, other):
+        return type(other) == IpRule and self.ty == other.ty and self.offset == other.offset and self.net == other.net and self.proto == other.proto
+
+    def __str__(self):
+        if self.proto == 4:
+            assert self.offset == 0
+            return f"""if ((ip->{self.ty} & MASK4({self.net.prefixlen})) != BIGEND32({int(self.net.network_address)}ULL))
+       break;"""
+        else:
+            u32s = [(int(self.net.network_address) >> (3*32)) & 0xffffffff,
+                    (int(self.net.network_address) >> (2*32)) & 0xffffffff,
+                    (int(self.net.network_address) >> (1*32)) & 0xffffffff,
+                    (int(self.net.network_address) >> (0*32)) & 0xffffffff]
+            if self.offset == 0:
+                mask = f"MASK6({self.net.prefixlen})"
+            else:
+                mask = f"MASK6_OFFS({self.offset}, {self.net.prefixlen})"
+            return f"""if ((ip6->{self.ty} & {mask}) != (BIGEND128({u32s[0]}ULL, {u32s[1]}ULL, {u32s[2]}ULL, {u32s[3]}ULL) & {mask}))
+       break;"""
 def ip_to_rule(proto, inip, ty, offset):
     if proto == 4:
         assert offset is None
         net = ipaddress.IPv4Network(inip.strip())
-        if net.prefixlen == 0:
-            return ""
-        return f"""if ((ip->{ty} & MASK4({net.prefixlen})) != BIGEND32({int(net.network_address)}ULL))
-       break;"""
+        return IpRule(ty, offset, net, 4)
     else:
         net = ipaddress.IPv6Network(inip.strip())
-        if net.prefixlen == 0:
-            return ""
-        u32s = [(int(net.network_address) >> (3*32)) & 0xffffffff,
-                (int(net.network_address) >> (2*32)) & 0xffffffff,
-                (int(net.network_address) >> (1*32)) & 0xffffffff,
-                (int(net.network_address) >> (0*32)) & 0xffffffff]
-        if offset is None:
-            mask = f"MASK6({net.prefixlen})"
-        else:
-            mask = f"MASK6_OFFS({offset}, {net.prefixlen})"
-        return f"""if ((ip6->{ty} & {mask}) != (BIGEND128({u32s[0]}ULL, {u32s[1]}ULL, {u32s[2]}ULL, {u32s[3]}ULL) & {mask}))
-       break;"""
+        return IpRule(ty, offset, net, 6)
 
 def fragment_to_rule(ipproto, rules):
     ast = parse_ast(rules, parse_frag_expr, False)
@@ -278,6 +321,37 @@ class RuleNode:
             assert type(action) == list
             assert type(inner) == RuleNode
 
+    def __lt__(self, other):
+        assert self.ty == RuleAction.CONDITIONS
+        assert other.ty == RuleAction.CONDITIONS
+
+        o = ORD_EQUAL
+
+        # RFC first has us sort by dest, then source, then other conditions. We don't implement the
+        # other conditions because doing so requires re-implementing the Flowspec wire format,
+        # which isn't trivial. However, we do implement the source/dest sorting in the hopes it
+        # allows us to group rules according to source/dest IP and hopefully LLVM optimizes out
+        # later rules.
+
+        selfdest = next(filter(lambda a : type(a) == IpRule and a.ty == "daddr", self.action), None)
+        otherdest = next(filter(lambda a : type(a) == IpRule and a.ty == "daddr", self.action), None)
+        if o == ORD_EQUAL and selfdest is not None and otherdest is not None:
+            o = selfdest.ord(otherdest)
+
+        if o == ORD_EQUAL:
+            selfsrc = next(filter(lambda a : type(a) == IpRule and a.ty == "saddr", self.action), None)
+            othersrc = next(filter(lambda a : type(a) == IpRule and a.ty == "saddr", self.action), None)
+            if selfsrc is not None and othersrc is None:
+                return True
+            elif selfsrc is None and othersrc is not None:
+                return False
+            elif selfsrc is not None and othersrc is not None:
+                o = selfsrc.ord(othersrc)
+
+        if o == ORD_LESS:
+            return True
+        return self.action < other.action
+
     def maybe_join(self, neighbor):
         if self.ty == RuleAction.CONDITIONS and neighbor.ty == RuleAction.CONDITIONS:
             overlapping_conditions = [x for x in self.action if x in neighbor.action]
@@ -311,7 +385,7 @@ class RuleNode:
         if self.ty == RuleAction.CONDITIONS:
             out.write(pfx + "do {\\\n")
             for cond in self.action:
-                out.write("\t" + pfx + cond.strip().replace("\n", " \\\n\t" + pfx) + " \\\n")
+                out.write("\t" + pfx + str(cond).replace("\n", " \\\n\t" + pfx) + " \\\n")
             self.inner.write(out, pfx)
             out.write(pfx + "} while(0);\\\n")
         elif self.ty == RuleAction.LIST:
@@ -384,7 +458,7 @@ with open("rules.h", "w") as out:
             conditions = []
             def write_rule(r):
                 global conditions
-                conditions.append(r + "\n")
+                conditions.append(r)
 
             rule = t[1].split("}")[0].strip()
             for step in rule.split(";"):
@@ -547,12 +621,12 @@ with open("rules.h", "w") as out:
     if ratelimitcnt != 0:
         out.write(f"#define RATE_CNT {ratelimitcnt}\n")
 
-    # Here we should probably sort the rules according to flowspec's sorting rules. We don't bother
-    # however, because its annoying.
-
     if len(rules4) != 0:
         out.write("#define NEED_V4_PARSE\n")
         out.write("#define RULES4 {\\\n")
+        # First sort the rules according to the RFC, then make it a single
+        # LIST rule and call flatten() to unify redundant conditions
+        rules4.sort()
         rules4 = RuleNode(RuleAction.LIST, None, rules4)
         rules4.flatten()
         rules4.write(out)
@@ -561,6 +635,9 @@ with open("rules.h", "w") as out:
     if len(rules6) != 0:
         out.write("#define NEED_V6_PARSE\n")
         out.write("#define RULES6 {\\\n")
+        # First sort the rules according to the RFC, then make it a single
+        # LIST rule and call flatten() to unify redundant conditions
+        rules6.sort()
         rules6 = RuleNode(RuleAction.LIST, None, rules6)
         rules6.flatten()
         rules6.write(out)

diff --git a/test.sh b/test.sh
index e17ec4bcc9a170ed9f946500f50c6ea91993174e..ad7a111bde187dddee74f9b19a658957e6bedb08 100755 (executable)
--- a/test.sh
+++ b/test.sh
@@ -2,9 +2,15 @@
 
 set -e
 
+# DROP, sample, and change DSCP
 COMMUNITY_DROP="
        Type: static univ
-       BGP.ext_community: (generic, 0x80060000, 0x0) (generic, 0x80070000, 0xf) (generic, 0x80090000, 0x3f)"
+       BGP.ext_community: (generic, 0x80060000, 0x0) (generic, 0x80070000, 0x3) (generic, 0x80090000, 0x3f)"
+# Sample and stop processing new rules
+COMMUNITY_TERMINAL_ACCEPT="
+       Type: static univ
+       BGP.ext_community: (generic, 0x80070000, 0x2)"
+
 
 DO_TEST() {
        clang -g -std=c99 -pedantic -Wall -Wextra -Wno-pointer-arith -Wno-unused-variable -Wno-unused-function -Wno-tautological-constant-out-of-range-compare -Wno-unused-function -Wno-visibility -O3 -emit-llvm -c xdp.c -o xdp.bc
@@ -93,6 +99,16 @@ DO_TEST XDP_DROP
 echo "flow6 { icmp code != 0; };$COMMUNITY_DROP" | ./genrules.py --ihl=drop-options --8021q=drop-vlan --v6frag=drop-frags
 DO_TEST XDP_PASS
 
+# Test ordering of source addresses. If we hit TERMINAL_ACCEPT first (cause its a more specific
+# prefix), then we'll pass, otherwise we'll drop.
+echo "flow6 { src 2a01:4f8:130:71d2::2/128; };$COMMUNITY_TERMINAL_ACCEPT
+flow6 { src 2a01::/16; }; $COMMUNITY_DROP" | ./genrules.py --ihl=accept-options --8021q=accept-vlan --v6frag=ignore
+DO_TEST XDP_PASS
+
+echo "flow6 { src 2a01::/16; };$COMMUNITY_TERMINAL_ACCEPT
+flow6 { src 2a01:4f8::/32; };$COMMUNITY_DROP" | ./genrules.py --ihl=accept-options --8021q=accept-vlan --v6frag=ignore
+DO_TEST XDP_DROP
+
 TEST_PKT='#define TEST \
 "\xcc\x2d\xe0\xf5\x02\xe1\x00\x0d\xb9\x50\x42\xfe\x81\x00\x00\x03" \
 "\x08\x00\x45\xfc\x00\x54\xda\x85\x40\x00\x40\x01\x67\xc6\x0a\x45" \