X-Git-Url: http://git.bitcoin.ninja/index.cgi?p=flowspec-xdp;a=blobdiff_plain;f=genrules.py;h=5d90e8c773a414b218a7db7be03f2b5eb3e085f9;hp=a84eacc7af0c6d51760f8bbc0fb171be9cda0faf;hb=ac33c8518d541b228fc24efcb89858abca0fc75f;hpb=ce7cb6545f4fd8872f08263733cb2188530e9420 diff --git a/genrules.py b/genrules.py index a84eacc..5d90e8c 100755 --- a/genrules.py +++ b/genrules.py @@ -45,20 +45,26 @@ class ASTNode: if self.action == ASTAction.EXPR: return self.left.write(expr_param, expr_param2) -def parse_ast(expr, parse_expr): +def parse_ast(expr, parse_expr, comma_is_or): expr = expr.strip() comma_split = expr.split(",", 1) or_split = expr.split("||", 1) if len(comma_split) > 1 and not "||" in comma_split[0]: - return ASTNode(ASTAction.OR, parse_ast(comma_split[0], parse_expr), parse_ast(comma_split[1], parse_expr)) + # Confusingly, BIRD uses `,` as either || or &&, depending on the type + # of expression being parsed. Specifically, a `numbers-match` uses `,` + # as OR, whereas a `bitmask-match` uses `,` as AND. + if comma_is_or: + return ASTNode(ASTAction.OR, parse_ast(comma_split[0], parse_expr, comma_is_or), parse_ast(comma_split[1], parse_expr, comma_is_or)) + else: + return ASTNode(ASTAction.AND, parse_ast(comma_split[0], parse_expr, comma_is_or), parse_ast(comma_split[1], parse_expr, comma_is_or)) if len(or_split) > 1: assert not "," in or_split[0] - return ASTNode(ASTAction.OR, parse_ast(or_split[0], parse_expr), parse_ast(or_split[1], parse_expr)) + return ASTNode(ASTAction.OR, parse_ast(or_split[0], parse_expr, comma_is_or), parse_ast(or_split[1], parse_expr, comma_is_or)) and_split = expr.split("&&", 1) if len(and_split) > 1: - return ASTNode(ASTAction.AND, parse_ast(and_split[0], parse_expr), parse_ast(and_split[1], parse_expr)) + return ASTNode(ASTAction.AND, parse_ast(and_split[0], parse_expr, comma_is_or), parse_ast(and_split[1], parse_expr, comma_is_or)) if expr.strip() == "true": return ASTNode(ASTAction.TRUE, None) @@ -66,7 +72,7 @@ def parse_ast(expr, parse_expr): return ASTNode(ASTAction.FALSE, None) if expr.startswith("!"): - return ASTNode(ASTAction.NOT, parse_ast(expr[1:], parse_expr)) + return ASTNode(ASTAction.NOT, parse_ast(expr[1:], parse_expr, comma_is_or)) return parse_expr(expr) @@ -193,15 +199,15 @@ def ip_to_rule(proto, inip, ty, offset): break;""" def fragment_to_rule(ipproto, rules): - ast = parse_ast(rules, parse_frag_expr) + ast = parse_ast(rules, parse_frag_expr, False) return "if (!( " + ast.write(ipproto) + " )) break;" def len_to_rule(rules): - ast = parse_ast(rules, parse_numbers_expr) + ast = parse_ast(rules, parse_numbers_expr, True) return "if (!( " + ast.write("(data_end - pktdata)") + " )) break;" def proto_to_rule(ipproto, proto): - ast = parse_ast(proto, parse_numbers_expr) + ast = parse_ast(proto, parse_numbers_expr, True) if ipproto == 4: return "if (!( " + ast.write("ip->protocol") + " )) break;" @@ -209,21 +215,21 @@ def proto_to_rule(ipproto, proto): return "if (!( " + ast.write("ip6->nexthdr") + " )) break;" def icmp_type_to_rule(proto, ty): - ast = parse_ast(ty, parse_numbers_expr) + ast = parse_ast(ty, parse_numbers_expr, True) if proto == 4: return "if (icmp == NULL) break;\nif (!( " + ast.write("icmp->type") + " )) break;" else: return "if (icmpv6 == NULL) break;\nif (!( " + ast.write("icmpv6->icmp6_type") + " )) break;" def icmp_code_to_rule(proto, code): - ast = parse_ast(code, parse_numbers_expr) + ast = parse_ast(code, parse_numbers_expr, True) if proto == 4: return "if (icmp == NULL) break;\nif (!( " + ast.write("icmp->code") + " )) break;" else: return "if (icmpv6 == NULL) break;\nif (!( " + ast.write("icmpv6->icmp6_code") + " )) break;" def dscp_to_rule(proto, rules): - ast = parse_ast(rules, parse_numbers_expr) + ast = parse_ast(rules, parse_numbers_expr, True) if proto == 4: return "if (!( " + ast.write("((ip->tos & 0xfc) >> 2)") + " )) break;" @@ -232,20 +238,20 @@ def dscp_to_rule(proto, rules): def port_to_rule(ty, rules): if ty == "port" : - ast = parse_ast(rules, parse_numbers_expr) - return "if (!ports_valid) break;\nif (!( " + ast.write("sport", "dport") + " )) break;" + ast = parse_ast(rules, parse_numbers_expr, True) + return "if (sport == -1 || dport == -1) break;\nif (!( " + ast.write("sport", "dport") + " )) break;" - ast = parse_ast(rules, parse_numbers_expr) - return "if (!ports_valid) break;\nif (!( " + ast.write(ty) + " )) break;" + ast = parse_ast(rules, parse_numbers_expr, True) + return "if (" + ty + " == -1) break;\nif (!( " + ast.write(ty) + " )) break;" def tcp_flags_to_rule(rules): - ast = parse_ast(rules, parse_bit_expr) + ast = parse_ast(rules, parse_bit_expr, False) return f"""if (tcp == NULL) break; if (!( {ast.write("(ntohs(tcp->flags) & 0xfff)")} )) break;""" def flow_label_to_rule(rules): - ast = parse_ast(rules, parse_bit_expr) + ast = parse_ast(rules, parse_bit_expr, False) return f"""if (ip6 == NULL) break; if (!( {ast.write("((((uint32_t)(ip6->flow_lbl[0] & 0xf)) << 2*8) | (((uint32_t)ip6->flow_lbl[1]) << 1*8) | (uint32_t)ip6->flow_lbl[0])")} )) break;""" @@ -290,6 +296,8 @@ with open("rules.h", "w") as out: use_v6_frags = False rulecnt = 0 ratelimitcnt = 0 + v4persrcratelimits = [] + v6persrcratelimits = [] lastrule = None for line in sys.stdin.readlines(): @@ -360,6 +368,7 @@ with open("rules.h", "w") as out: # Now write the match handling! first_action = None + stats_action = None last_action = None for community in line.split("("): if not community.startswith("generic, "): @@ -369,57 +378,97 @@ with open("rules.h", "w") as out: if len(blocks[1].strip()) != 10: # Should be 0x12345678 continue ty = blocks[1].strip()[:6] + high_byte = int(blocks[1].strip()[6:8], 16) + mid_byte = int(blocks[1].strip()[8:], 16) low_bytes = int(blocks[2].strip(") \n"), 16) - if ty == "0x8006": + if ty == "0x8006" or ty == "0x800c" or ty == "0x8306" or ty == "0x830c": if first_action is not None: - assert False # Two ratelimit actions? + # Two ratelimit actions, just drop the old one. RFC 8955 says we can. + first_action = None + exp = (low_bytes & (0xff << 23)) >> 23 if low_bytes == 0: - first_action = "return XDP_DROP;" + first_action = "{stats_replace}\nreturn XDP_DROP;" + elif low_bytes & (1 << 31) != 0: + # Negative limit, just drop + first_action = "{stats_replace}\nreturn XDP_DROP;" + elif exp == 0xff: + # NaN/INF. Just treat as INF and accept + first_action = None + elif exp <= 127: # < 1 + first_action = "{stats_replace}\nreturn XDP_DROP;" + elif exp >= 127 + 63: # The count won't even fit in 64-bits, just accept + first_action = None else: - if low_bytes & (1 << 31) != 0: - assert False # Negative ratelimit? - exp = (low_bytes & (0xff << 23)) >> 23 - if exp == 0xff: - assert False # NaN/INF? - if exp <= 127: # < 1 - first_action = "return XDP_DROP;" - if exp >= 127 + 63: # The count won't even fit in 64-bits, just accept - first_action = "return XDP_PASS;" mantissa = low_bytes & ((1 << 23) - 1) value = 1.0 + mantissa / (2**23) value *= 2**(exp-127) + if ty == "0x8006" or ty == "0x8306": + accessor = "rate->rate.sent_bytes" + else: + accessor = "rate->rate.sent_packets" # Note that int64_t will overflow after 292 years of uptime first_action = "int64_t time = bpf_ktime_get_ns();\n" - first_action += f"const uint32_t ratelimitidx = {ratelimitcnt};\n" - first_action += "size_t pktlen = data_end - pktdata;\n" - first_action += "uint64_t extra_bytes = 0;\n" - first_action += "struct ratelimit *rate = bpf_map_lookup_elem(&rate_map, &ratelimitidx);\n" - first_action += "if (rate) {\n" - first_action += "\tbpf_spin_lock(&rate->lock);\n" - first_action += "\tif (likely(rate->sent_bytes > 0)) {\n" - first_action += "\t\tint64_t diff = time - rate->sent_time;\n" + first_action += "uint64_t allowed_since_last = 0;\n" + if ty == "0x8006" or ty == "0x800c": + spin_lock = "bpf_spin_lock(&rate->lock);" + spin_unlock = "bpf_spin_unlock(&rate->lock);" + first_action += f"const uint32_t ratelimitidx = {ratelimitcnt};\n" + first_action += "struct ratelimit *rate = bpf_map_lookup_elem(&rate_map, &ratelimitidx);\n" + ratelimitcnt += 1 + else: + spin_lock = "/* No locking as we're per-CPU */" + spin_unlock = "/* No locking as we're per-CPU */" + if proto == 4: + if mid_byte > 32: + continue + first_action += f"const uint32_t srcip = ip->saddr & MASK4({mid_byte});\n" + first_action += f"void *rate_map = &v4_src_rate_{len(v4persrcratelimits)};\n" + v4persrcratelimits.append((high_byte + 1) * 1024) + else: + if mid_byte > 128: + continue + first_action += f"const uint128_t srcip = ip6->saddr & MASK6({mid_byte});\n" + first_action += f"void *rate_map = &v6_src_rate_{len(v6persrcratelimits)};\n" + v6persrcratelimits.append((high_byte + 1) * 1024) + first_action += f"struct percpu_ratelimit *rate = bpf_map_lookup_elem(rate_map, &srcip);\n" + first_action += "if (rate) {\n" + first_action += f"\t{spin_lock}\n" + first_action += f"\tif (likely({accessor} > 0))" + " {\n" + first_action += "\t\tint64_t diff = time - rate->sent_time;\n" # Unlikely or not, if the flow is slow, take a perf hit (though with the else if branch it doesn't matter) - first_action += "\t\tif (unlikely(diff > 1000000000))\n" - first_action += "\t\t\trate->sent_bytes = 0;\n" - first_action += "\t\telse if (likely(diff > 0))\n" - first_action += f"\t\t\textra_bytes = ((uint64_t)diff) * {math.floor(value)} / 1000000000;\n" - first_action += "\t}\n" - first_action += "\tif (rate->sent_bytes - ((int64_t)extra_bytes) <= 0) {\n" - first_action += "\t\trate->sent_bytes = data_end - pktdata;\n" - first_action += "\t\trate->sent_time = time;\n" - first_action += "\t\tbpf_spin_unlock(&rate->lock);\n" - first_action += "\t} else {\n" - first_action += "\t\tbpf_spin_unlock(&rate->lock);\n" - first_action += "\t\treturn XDP_DROP;\n" - first_action += "\t}\n" - first_action += "}\n" - ratelimitcnt += 1 + first_action += "\t\tif (unlikely(diff > 1000000000))\n" + first_action += f"\t\t\t{accessor} = 0;\n" + first_action += "\t\telse if (likely(diff > 0))\n" + first_action += f"\t\t\tallowed_since_last = ((uint64_t)diff) * {math.floor(value)} / 1000000000;\n" + first_action += "\t}\n" + first_action += f"\tif ({accessor} - ((int64_t)allowed_since_last) <= 0)" + " {\n" + if ty == "0x8006" or ty == "0x8306": + first_action += f"\t\t{accessor} = data_end - pktdata;\n" + else: + first_action += f"\t\t{accessor} = 1;\n" + first_action += "\t\trate->sent_time = time;\n" + first_action += f"\t\t{spin_unlock}\n" + first_action += "\t} else {\n" + first_action += f"\t\t{spin_unlock}\n" + first_action += "\t\t{stats_replace}\n" + first_action += "\t\treturn XDP_DROP;\n" + first_action += "\t}\n" + if ty == "0x8306" or ty == "0x830c": + first_action += "} else {\n" + first_action += "\tstruct percpu_ratelimit new_rate = { .sent_time = time, };\n" + first_action += "\trate = &new_rate;\n" + if ty == "0x8006" or ty == "0x8306": + first_action += f"\t\t{accessor} = data_end - pktdata;\n" + else: + first_action += f"\t\t{accessor} = 1;\n" + first_action += "\tbpf_map_update_elem(rate_map, &srcip, rate, BPF_ANY);\n" + first_action += "}\n" elif ty == "0x8007": if low_bytes & 1 == 0: last_action = "return XDP_PASS;" if low_bytes & 2 == 2: - write_rule(f"const uint32_t ruleidx = STATIC_RULE_CNT + {rulecnt};") - write_rule("INCREMENT_MATCH(ruleidx);") + stats_action = f"const uint32_t ruleidx = STATIC_RULE_CNT + {rulecnt};\n" + stats_action += "INCREMENT_MATCH(ruleidx);" elif ty == "0x8008": assert False # We do not implement the redirect action elif ty == "0x8009": @@ -430,13 +479,16 @@ with open("rules.h", "w") as out: write_rule("uint8_t orig_tos = ip->tos;") write_rule("ip->tos = (ip->tos & 3) | " + str(low_bytes << 2) + ";") write_rule("chk = (chk - orig_tos + ip->tos);") - write_rule("if (unlikely(chk < 0)) { chk += 65534; }") + write_rule("if (unlikely(chk > 0xffff)) { chk -= 65535; }") + write_rule("else if (unlikely(chk < 0)) { chk += 65535; }") write_rule("ip->check = ~BE16(chk);") else: write_rule("ip6->priority = " + str(low_bytes >> 2) + ";") write_rule("ip6->flow_lbl[0] = (ip6->flow_lbl[0] & 0x3f) | " + str((low_bytes & 3) << 6) + ";") if first_action is not None: - write_rule(first_action) + write_rule(first_action.replace("{stats_replace}", stats_action)) + if stats_action is not None and (first_action is None or "{stats_replace}" not in first_action): + write_rule(stats_action) if last_action is not None: write_rule(last_action) if proto == 6: @@ -459,3 +511,8 @@ with open("rules.h", "w") as out: if args.v6frag == "ignore-parse-if-rule": if use_v6_frags: out.write("#define PARSE_V6_FRAG PARSE\n") + with open("maps.h", "w") as out: + for idx, limit in enumerate(v4persrcratelimits): + out.write(f"V4_SRC_RATE_DEFINE({idx}, {limit})\n") + for idx, limit in enumerate(v6persrcratelimits): + out.write(f"V6_SRC_RATE_DEFINE({idx}, {limit})\n")