From 80e92801d22e22493f9f0505a8ed06e6ca95716d Mon Sep 17 00:00:00 2001 From: Matt Corallo Date: Tue, 14 Sep 2021 18:02:47 +0000 Subject: [PATCH] Reuse hash table bucket entries if they're stale 32+ seconds --- genrules.py | 12 ++++++------ xdp.c | 15 +++++++++++++-- 2 files changed, 19 insertions(+), 8 deletions(-) diff --git a/genrules.py b/genrules.py index 93c22f5..3f901e1 100755 --- a/genrules.py +++ b/genrules.py @@ -404,7 +404,7 @@ with open("rules.h", "w") as out: value = 1.0 + mantissa / (2**23) value *= 2**(exp-127) - first_action = "int64_t time = bpf_ktime_get_ns() & RATE_TIME_MASK;\n" + first_action = "int64_t time_masked = bpf_ktime_get_ns() & RATE_TIME_MASK;\n" first_action += f"int64_t per_pkt_ns = (1000000000LL << RATE_BUCKET_INTEGER_BITS) / {math.floor(value)};\n" if ty == "0x8006" or ty == "0x800c": spin_lock = "bpf_spin_lock(&rate->lock);" @@ -420,13 +420,13 @@ with open("rules.h", "w") as out: 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" - first_action += f"struct persrc_rate4_ptr rate_ptr = get_v4_persrc_ratelimit(srcip, rate_map, {(high_byte + 1) * 4096});\n" + first_action += f"struct persrc_rate4_ptr rate_ptr = get_v4_persrc_ratelimit(srcip, rate_map, {(high_byte + 1) * 4096}, time_masked);\n" first_action += f"struct persrc_rate4_entry *rate = rate_ptr.rate;\n" v4persrcratelimits.append((high_byte + 1) * 4096) elif mid_byte <= 64: first_action += f"const uint64_t srcip = BE128BEHIGH64(ip6->saddr & MASK6({mid_byte}));\n" first_action += f"void *rate_map = &v5_src_rate_{len(v5persrcratelimits)};\n" - first_action += f"struct persrc_rate5_ptr rate_ptr = get_v5_persrc_ratelimit(srcip, rate_map, {(high_byte + 1) * 4096});\n" + first_action += f"struct persrc_rate5_ptr rate_ptr = get_v5_persrc_ratelimit(srcip, rate_map, {(high_byte + 1) * 4096}, time_masked);\n" first_action += f"struct persrc_rate5_entry *rate = rate_ptr.rate;\n" v5persrcratelimits.append((high_byte + 1) * 4096) else: @@ -434,7 +434,7 @@ with open("rules.h", "w") as out: 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" - first_action += f"struct persrc_rate6_ptr rate_ptr = get_v6_persrc_ratelimit(srcip, rate_map, {(high_byte + 1) * 4096});\n" + first_action += f"struct persrc_rate6_ptr rate_ptr = get_v6_persrc_ratelimit(srcip, rate_map, {(high_byte + 1) * 4096}, time_masked);\n" first_action += f"struct persrc_rate6_entry *rate = rate_ptr.rate;\n" v6persrcratelimits.append((high_byte + 1) * 4096) if ty == "0x8006" or ty == "0x8306": @@ -445,7 +445,7 @@ with open("rules.h", "w") as out: first_action += f"\t{spin_lock}\n" first_action += "\tint64_t bucket_pkts = (rate->sent_time & (~RATE_TIME_MASK)) >> (64 - RATE_BUCKET_BITS);\n" # We mask the top 12 bits, so date overflows every 52 days, handled below - first_action += "\tint64_t time_diff = time - ((int64_t)(rate->sent_time & RATE_TIME_MASK));\n" + first_action += "\tint64_t time_diff = time_masked - ((int64_t)(rate->sent_time & RATE_TIME_MASK));\n" first_action += "\tif (unlikely(time_diff < -1000000000 || time_diff > 16000000000)) {\n" first_action += "\t\tbucket_pkts = 0;\n" first_action += "\t} else {\n" @@ -459,7 +459,7 @@ with open("rules.h", "w") as out: first_action += "\t\treturn XDP_DROP;\n" first_action += "\t} else {\n" first_action += "\t\tif (unlikely(bucket_pkts < 0)) bucket_pkts = 0;\n" - first_action += f"\t\trate->sent_time = time | ((bucket_pkts + (1 << RATE_BUCKET_DECIMAL_BITS)) << (64 - RATE_BUCKET_BITS));\n" + first_action += f"\t\trate->sent_time = time_masked | ((bucket_pkts + (1 << RATE_BUCKET_DECIMAL_BITS)) << (64 - RATE_BUCKET_BITS));\n" first_action += f"\t\t{spin_unlock}\n" first_action += "\t}\n" first_action += "}\n" diff --git a/xdp.c b/xdp.c index 6a8c19e..ad6ab82 100644 --- a/xdp.c +++ b/xdp.c @@ -185,6 +185,11 @@ struct { #define RATE_BUCKET_BITS (RATE_BUCKET_DECIMAL_BITS + RATE_BUCKET_INTEGER_BITS) #define RATE_TIME_MASK ((1ULL << (64 - RATE_BUCKET_BITS)) - 1) +// Time going backwards 10ms+ or forward 32sec+ implies we should consider it +// an overflow, or at least stale enough that we should reset the entry. +#define RATE_MIN_TIME_OFFSET -10000000LL +#define RATE_MAX_TIME_OFFSET 32000000000LL + #ifdef RATE_CNT struct ratelimit { struct bpf_spin_lock lock; @@ -232,7 +237,7 @@ struct persrc_rate##IPV##_ptr { \ }; \ \ __attribute__((always_inline)) \ -static inline struct persrc_rate##IPV##_ptr get_v##IPV##_persrc_ratelimit(IP_TYPE key, void *map, size_t map_limit) { \ +static inline struct persrc_rate##IPV##_ptr get_v##IPV##_persrc_ratelimit(IP_TYPE key, void *map, size_t map_limit, int64_t cur_time_masked) { \ struct persrc_rate##IPV##_ptr res = { .rate = NULL, .lock = NULL }; \ uint64_t hash = siphash(&key, sizeof(key), COMPILE_TIME_RAND); \ \ @@ -253,7 +258,13 @@ static inline struct persrc_rate##IPV##_ptr get_v##IPV##_persrc_ratelimit(IP_TYP res.rate = &first_bucket[i]; \ res.lock = &buckets->lock; \ return res; \ - } else if (min_sent_time > (first_bucket[i].sent_time & RATE_TIME_MASK)) { \ + } \ + int64_t time_offset = ((int64_t)cur_time_masked) - (first_bucket[i].sent_time & RATE_TIME_MASK); \ + if (time_offset < RATE_MIN_TIME_OFFSET || time_offset > RATE_MAX_TIME_OFFSET) { \ + min_sent_idx = i; \ + break; \ + } \ + if ((first_bucket[i].sent_time & RATE_TIME_MASK) < min_sent_time) { \ min_sent_time = first_bucket[i].sent_time & RATE_TIME_MASK; \ min_sent_idx = i; \ } \ -- 2.30.2