+ 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)
+ # 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"
+ # 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