From: Matt Corallo <git@bluematt.me>
Date: Tue, 6 Apr 2021 02:40:24 +0000 (-0400)
Subject: Support ratelimiting communities
X-Git-Url: http://git.bitcoin.ninja/?a=commitdiff_plain;h=c5f8e7b221515ce043779456945d45a7098d9d9e;p=flowspec-xdp

Support ratelimiting communities
---

diff --git a/genrules.py b/genrules.py
index 51e547d..300900a 100755
--- a/genrules.py
+++ b/genrules.py
@@ -4,6 +4,7 @@ import sys
 import ipaddress
 from enum import Enum
 import argparse
+import math
 
 
 IP_PROTO_ICMP = 1
@@ -288,6 +289,7 @@ with open("rules.h", "w") as out:
     rules4 = ""
     use_v6_frags = False
     rulecnt = 0
+    ratelimitcnt = 0
 
     lastrule = None
     for line in sys.stdin.readlines():
@@ -369,10 +371,38 @@ with open("rules.h", "w") as out:
                 ty = blocks[1].strip()[:6]
                 low_bytes = int(blocks[2].strip(") \n"), 16)
                 if ty == "0x8006":
+                    if first_action is not None:
+                        assert False # Two ratelimit actions?
                     if low_bytes == 0:
                         first_action = "return XDP_DROP;"
                     else:
-                        assert False # Not yet supported
+                        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)
+                        first_action = "uint64_t secs = bpf_ktime_get_ns() / 1000000000;\n"
+                        first_action += f"const uint32_t ratelimitidx = {ratelimitcnt};\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 += "\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":
                     if low_bytes & 1 == 0:
                         last_action = "return XDP_PASS;"
@@ -407,6 +437,8 @@ with open("rules.h", "w") as out:
 
     out.write("\n")
     out.write(f"#define RULECNT {rulecnt}\n")
+    if ratelimitcnt != 0:
+        out.write(f"#define RATE_CNT {ratelimitcnt}\n")
     if rules4 != "":
         out.write("#define NEED_V4_PARSE\n")
         out.write("#define RULES4 {\\\n" + rules4 + "}\n")
diff --git a/install.sh b/install.sh
index af9a3ed..58ae670 100755
--- a/install.sh
+++ b/install.sh
@@ -5,7 +5,7 @@ RULES="$(birdc show route table flowspec4 primary all)
 $(birdc show route table flowspec6 primary all)"
 
 echo "$RULES" | ./genrules.py --8021q=drop-vlan --v6frag=ignore-parse-if-rule --ihl=drop-options
-clang -std=c99 -pedantic -Wall -Wextra -Wno-pointer-arith -Wno-unused-variable -O3 -emit-llvm -c xdp.c -o - | llc -O3 -march=bpf -filetype=obj -o xdp
+clang -g -std=c99 -pedantic -Wall -Wextra -Wno-pointer-arith -Wno-unused-variable -O3 -emit-llvm -c xdp.c -o - | llc -O3 -march=bpf -filetype=obj -o xdp
 
 echo "Before unload drop count was:"
 ./dropcount.sh || echo "Not loaded"
diff --git a/xdp.c b/xdp.c
index 3ebec88..d9aa076 100644
--- a/xdp.c
+++ b/xdp.c
@@ -162,6 +162,20 @@ struct bpf_map_def SEC("maps") drop_cnt_map = {
 		*value += 1; \
 }
 
+#ifdef RATE_CNT
+struct ratelimit {
+	struct bpf_spin_lock lock;
+	uint64_t bucket_secs;
+	uint64_t bucket_count;
+};
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, RATE_CNT);
+	__u32 *key;
+	struct ratelimit *value;
+} rate_map SEC(".maps");
+#endif
+
 SEC("xdp_drop")
 #endif
 int xdp_drop_prog(struct xdp_md *ctx)