Tag short packets as unlikely

diff --git a/xdp.c b/xdp.c
index 8623af44c1f0cdbb6b0591e7d4c6db148cf05739..26a12313097539af3477af65dece5d8945016d98 100644 (file)
--- a/xdp.c
+++ b/xdp.c
@@ -108,6 +108,9 @@ struct tcphdr {
 // Note rules.h may also define PARSE_IHL
 #include "rules.h"
 
+#define unlikely(a) __builtin_expect(a, 0)
+#define likely(a) __builtin_expect(a, 1)
+
 #ifdef TEST
 // 64 bit version of xdp_md for testing
 struct xdp_md {
@@ -136,18 +139,18 @@ int xdp_drop_prog(struct xdp_md *ctx)
        unsigned short eth_proto;
 
        {
-               if ((void*)(size_t)ctx->data + sizeof(struct ethhdr) > data_end)
+               if (unlikely((void*)(size_t)ctx->data + sizeof(struct ethhdr) > data_end))
                        return XDP_DROP;
                const struct ethhdr *const eth = (void*)(size_t)ctx->data;
 
 #ifdef PARSE_8021Q
-               if (eth->h_proto == BE16(ETH_P_8021Q)) {
-                       if ((void*)(size_t)ctx->data + sizeof(struct ethhdr_vlan) > data_end)
+               if (likely(eth->h_proto == BE16(ETH_P_8021Q))) {
+                       if (unlikely((void*)(size_t)ctx->data + sizeof(struct ethhdr_vlan) > data_end))
                                return XDP_DROP;
                        const struct ethhdr_vlan *const eth_vlan = (void*)(size_t)ctx->data;
 
 #ifdef REQ_8021Q
-                       if ((eth_vlan->tci & BE16(0xfff)) != BE16(REQ_8021Q))
+                       if (unlikely((eth_vlan->tci & BE16(0xfff)) != BE16(REQ_8021Q)))
                                return XDP_DROP;
 #endif
 
@@ -176,32 +179,32 @@ int xdp_drop_prog(struct xdp_md *ctx)
        const struct ip6hdr *ip6 = NULL;
        const void *l4hdr = NULL;
        if (eth_proto == BE16(ETH_P_IP)) {
-               if (pktdata + sizeof(struct iphdr) > data_end)
+               if (unlikely(pktdata + sizeof(struct iphdr) > data_end))
                        return XDP_DROP;
                ip = (struct iphdr*) pktdata;
 
 #ifdef PARSE_IHL
-               if (ip->ihl < 5) return XDP_DROP;
+               if (unlikely(ip->ihl < 5)) return XDP_DROP;
                l4hdr = pktdata + ip->ihl * 4;
 #else
                if (ip->ihl != 5) return XDP_DROP;
                l4hdr = pktdata + 5*4;
 #endif
                if (ip->protocol == IP_PROTO_TCP) {
-                       if (l4hdr + sizeof(struct tcphdr) > data_end)
+                       if (unlikely(l4hdr + sizeof(struct tcphdr) > data_end))
                                return XDP_DROP;
                        tcp = (struct tcphdr*) l4hdr;
                } else if (ip->protocol == IP_PROTO_UDP) {
-                       if (l4hdr + sizeof(struct udphdr) > data_end)
+                       if (unlikely(l4hdr + sizeof(struct udphdr) > data_end))
                                return XDP_DROP;
                        udp = (struct udphdr*) l4hdr;
                } else if (ip->protocol == IP_PROTO_ICMP) {
-                       if (l4hdr + sizeof(struct icmphdr) > data_end)
+                       if (unlikely(l4hdr + sizeof(struct icmphdr) > data_end))
                                return XDP_DROP;
                        icmp = (struct icmphdr*) l4hdr;
                }
        } else if (eth_proto == BE16(ETH_P_IPV6)) {
-               if (pktdata + sizeof(struct ip6hdr) > data_end)
+               if (unlikely(pktdata + sizeof(struct ip6hdr) > data_end))
                        return XDP_DROP;
                ip6 = (struct ip6hdr*) pktdata;
 
@@ -209,7 +212,7 @@ int xdp_drop_prog(struct xdp_md *ctx)
 
                uint8_t v6nexthdr;
                if (ip6->nexthdr == IP6_PROTO_FRAG) {
-                       if (l4hdr + sizeof(struct ip6_fraghdr) > data_end)
+                       if (unlikely(l4hdr + sizeof(struct ip6_fraghdr) > data_end))
                                return XDP_DROP;
                        frag6 = (struct ip6_fraghdr*) l4hdr;
                        l4hdr = l4hdr + sizeof(struct ip6_fraghdr);
@@ -219,15 +222,15 @@ int xdp_drop_prog(struct xdp_md *ctx)
                }
 
                if (v6nexthdr == IP_PROTO_TCP) {
-                       if (l4hdr + sizeof(struct tcphdr) > data_end)
+                       if (unlikely(l4hdr + sizeof(struct tcphdr) > data_end))
                                return XDP_DROP;
                        tcp = (struct tcphdr*) l4hdr;
                } else if (v6nexthdr == IP_PROTO_UDP) {
-                       if (l4hdr + sizeof(struct udphdr) > data_end)
+                       if (unlikely(l4hdr + sizeof(struct udphdr) > data_end))
                                return XDP_DROP;
                        udp = (struct udphdr*) l4hdr;
                } else if (v6nexthdr == IP6_PROTO_ICMPV6) {
-                       if (l4hdr + sizeof(struct icmp6hdr) > data_end)
+                       if (unlikely(l4hdr + sizeof(struct icmp6hdr) > data_end))
                                return XDP_DROP;
                        icmpv6 = (struct icmp6hdr*) l4hdr;
                }