From: Matt Corallo Date: Fri, 9 Apr 2021 17:29:11 +0000 (-0400) Subject: Handle packet rate limits, too X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=0a516f6c712109cbaad8324964c94197dd8c85e5;p=flowspec-xdp Handle packet rate limits, too --- diff --git a/genrules.py b/genrules.py index a84eacc..db138a8 100755 --- a/genrules.py +++ b/genrules.py @@ -370,49 +370,58 @@ with open("rules.h", "w") as out: continue ty = blocks[1].strip()[:6] low_bytes = int(blocks[2].strip(") \n"), 16) - if ty == "0x8006": + if ty == "0x8006" or ty == "0x800c": 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;" + elif low_bytes & (1 << 31) != 0: + # Negative limit, just drop + first_action = "return XDP_DROP;" + elif exp == 0xff: + # NaN/INF. Just treat as INF and accept + first_action = None + elif exp <= 127: # < 1 + first_action = "return 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": + 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" + 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 += 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" + 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": + 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 += "\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 elif ty == "0x8007": if low_bytes & 1 == 0: diff --git a/xdp.c b/xdp.c index 506d422..fc8f2c3 100644 --- a/xdp.c +++ b/xdp.c @@ -172,7 +172,10 @@ struct { #ifdef RATE_CNT struct ratelimit { struct bpf_spin_lock lock; - int64_t sent_bytes; + union { + int64_t sent_bytes; + int64_t sent_packets; + } rate; int64_t sent_time; }; struct {