From 3a4f945c529523a181916300196e6314e0c5f63b Mon Sep 17 00:00:00 2001 From: Matt Corallo Date: Thu, 9 Dec 2021 22:51:51 +0000 Subject: [PATCH] Partially implement sorting --- README.md | 6 +-- genrules.py | 119 ++++++++++++++++++++++++++++++++++++++++++---------- test.sh | 18 +++++++- 3 files changed, 118 insertions(+), 25 deletions(-) diff --git a/README.md b/README.md index 5f6e917..9ed1c18 100644 --- 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 3865b6b..a9f3d16 100755 --- 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 e17ec4b..ad7a111 100755 --- 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" \ -- 2.39.5