From ce7cb6545f4fd8872f08263733cb2188530e9420 Mon Sep 17 00:00:00 2001 From: Matt Corallo Date: Tue, 6 Apr 2021 10:05:07 -0400 Subject: [PATCH] Less effecient, but much, much less naive rate-limiter --- genrules.py | 27 +++++++++++++++++++-------- xdp.c | 4 ++-- 2 files changed, 21 insertions(+), 10 deletions(-) diff --git a/genrules.py b/genrules.py index 300900a..a84eacc 100755 --- a/genrules.py +++ b/genrules.py @@ -388,19 +388,30 @@ with open("rules.h", "w") as out: mantissa = low_bytes & ((1 << 23) - 1) value = 1.0 + mantissa / (2**23) value *= 2**(exp-127) - first_action = "uint64_t secs = bpf_ktime_get_ns() / 1000000000;\n" + # 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 (secs != rate->bucket_secs) {\n" - first_action += "\t\trate->bucket_secs = secs;\n" - first_action += "\t\trate->bucket_count = 0;\n" + first_action += "\tif (likely(rate->sent_bytes > 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 += f"\tif (rate->bucket_count + (data_end - pktdata) > {math.floor(value)})\n" - first_action += "\t\t{ bpf_spin_unlock(&rate->lock); return XDP_DROP; }\n" - first_action += "\trate->bucket_count += data_end - pktdata;\n" - first_action += "\tbpf_spin_unlock(&rate->lock);\n" first_action += "}\n" ratelimitcnt += 1 elif ty == "0x8007": diff --git a/xdp.c b/xdp.c index d9aa076..8003b89 100644 --- a/xdp.c +++ b/xdp.c @@ -165,8 +165,8 @@ struct bpf_map_def SEC("maps") drop_cnt_map = { #ifdef RATE_CNT struct ratelimit { struct bpf_spin_lock lock; - uint64_t bucket_secs; - uint64_t bucket_count; + int64_t sent_bytes; + int64_t sent_time; }; struct { __uint(type, BPF_MAP_TYPE_ARRAY); -- 2.39.5