Reuse hash table bucket entries if they're stale 32+ seconds

diff --git a/genrules.py b/genrules.py
index 93c22f5c9059dfb7f7cccefa7707dda1fb849871..3f901e1c908a1595e35264279016e01e37874c7c 100755 (executable)
--- 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 6a8c19e4f852bad1e108093332043d0033f8e55b..ad6ab82db97feedc53f88f9f9f3f067d65bcbb7f 100644 (file)
--- 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; \
                } \