Only parse v4/v6 if we have relevant rules for them

diff --git a/genrules.py b/genrules.py
index c0a5311916f6f25536848a21c3a5061be547bab5..82b8d8225cc0ab34161397e1cf17691df44f4e0b 100755 (executable)
--- a/genrules.py
+++ b/genrules.py
@@ -261,6 +261,9 @@ with open("rules.h", "w") as out:
             assert False
         out.write("#define REQ_8021Q " + args.vlan_tag + "\n")
 
+    use_v4 = False
+    use_v6 = False
+
     out.write("#define RULES \\\n")
 
     def write_rule(r):
@@ -272,10 +275,12 @@ with open("rules.h", "w") as out:
             continue
         if t[0].strip() == "flow4":
             proto = 4
+            use_v4 = True
             out.write("if (eth_proto == htons(ETH_P_IP)) { \\\n")
             out.write("\tdo {\\\n")
         elif t[0].strip() == "flow6":
             proto = 6
+            use_v6 = True
             out.write("if (eth_proto == htons(ETH_P_IPV6)) { \\\n")
             out.write("\tdo {\\\n")
         else:
@@ -322,3 +327,7 @@ with open("rules.h", "w") as out:
         out.write("\t} while(0);\\\n}\\\n")
 
     out.write("\n")
+    if use_v4:
+        out.write("#define NEED_V4_PARSE\n")
+    if use_v6:
+        out.write("#define NEED_V6_PARSE\n")

diff --git a/xdp.c b/xdp.c
index 669d3ebfa365f13feee331258df4b4434e3cc5ab..b93b16936bdfdde7f72d6e84277a95cda8e501cf 100644 (file)
--- a/xdp.c
+++ b/xdp.c
@@ -170,14 +170,21 @@ int xdp_drop_prog(struct xdp_md *ctx)
                }
        }
 
-       const struct tcphdr *tcp = NULL;
-       const struct udphdr *udp = NULL;
+#ifdef NEED_V4_PARSE
+       const struct iphdr *ip = NULL;
        const struct icmphdr *icmp = NULL;
+#endif
+#ifdef NEED_V6_PARSE
+       const struct ip6hdr *ip6 = NULL;
        const struct icmp6hdr *icmpv6 = NULL;
        const struct ip6_fraghdr *frag6 = NULL;
-       const struct iphdr *ip = NULL;
-       const struct ip6hdr *ip6 = NULL;
+#endif
+
        const void *l4hdr = NULL;
+       const struct tcphdr *tcp = NULL;
+       const struct udphdr *udp = NULL;
+
+#ifdef NEED_V4_PARSE
        if (eth_proto == BE16(ETH_P_IP)) {
                if (unlikely(pktdata + sizeof(struct iphdr) > data_end))
                        return XDP_DROP;
@@ -204,7 +211,10 @@ int xdp_drop_prog(struct xdp_md *ctx)
                                return XDP_DROP;
                        icmp = (struct icmphdr*) l4hdr;
                }
-       } else if (eth_proto == BE16(ETH_P_IPV6)) {
+       }
+#endif
+#ifdef NEED_V6_PARSE
+       if (eth_proto == BE16(ETH_P_IPV6)) {
                if (unlikely(pktdata + sizeof(struct ip6hdr) > data_end))
                        return XDP_DROP;
                ip6 = (struct ip6hdr*) pktdata;
@@ -236,9 +246,8 @@ int xdp_drop_prog(struct xdp_md *ctx)
                        icmpv6 = (struct icmp6hdr*) l4hdr;
                }
                // TODO: Handle some options?
-       } else {
-               return XDP_PASS;
        }
+#endif
 
        uint16_t sport, dport; // Host Endian! Only valid with tcp || udp
        if (tcp != NULL) {