X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=xdp.c;h=4e4d6c6308437ed759239c1f166f982dca36256c;hb=d4d0eb34912fd66bf9eb73d98ed57fd3def3336a;hp=1709e00cfb727e308c541d60441c8ce50c828707;hpb=66e2db182f749072cac361b873dcc35d6377468e;p=flowspec-xdp

diff --git a/xdp.c b/xdp.c
index 1709e00..4e4d6c6 100644
--- a/xdp.c
+++ b/xdp.c
@@ -159,6 +159,12 @@ struct bpf_map_def SEC("maps") drop_cnt_map = {
 
 SEC("xdp_drop")
 #endif
+
+// It seems (based on drop counts) that data_end points to the last byte, not one-past-the-end.
+// This feels strange, but some documentation suggests > here as well, so we stick with that.
+#define CHECK_LEN(start, struc) \
+	if (unlikely((void*)(start) + sizeof(struct struc) > data_end)) DO_RETURN(PKT_LEN_DROP, XDP_DROP);
+
 int xdp_drop_prog(struct xdp_md *ctx)
 {
 	const void *const data_end = (void *)(size_t)ctx->data_end;
@@ -167,14 +173,12 @@ int xdp_drop_prog(struct xdp_md *ctx)
 	unsigned short eth_proto;
 
 	{
-		if (unlikely((void*)(size_t)ctx->data + sizeof(struct ethhdr) > data_end))
-			DO_RETURN(PKT_LEN_DROP, XDP_DROP);
+		CHECK_LEN((size_t)ctx->data, ethhdr);
 		const struct ethhdr *const eth = (void*)(size_t)ctx->data;
 
 #if PARSE_8021Q == PARSE
 		if (likely(eth->h_proto == BE16(ETH_P_8021Q))) {
-			if (unlikely((void*)(size_t)ctx->data + sizeof(struct ethhdr_vlan) > data_end))
-				DO_RETURN(PKT_LEN_DROP, XDP_DROP);
+			CHECK_LEN((size_t)ctx->data, ethhdr_vlan);
 			const struct ethhdr_vlan *const eth_vlan = (void*)(size_t)ctx->data;
 
 #ifdef REQ_8021Q
@@ -198,25 +202,15 @@ int xdp_drop_prog(struct xdp_md *ctx)
 		}
 	}
 
-#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;
-#endif
-
 	const void *l4hdr = NULL;
 	const struct tcphdr *tcp = NULL;
-	const struct udphdr *udp = NULL;
+	uint8_t ports_valid = 0;
+	uint16_t sport, dport; // Host Endian! Only valid with tcp || udp
 
 #ifdef NEED_V4_PARSE
 	if (eth_proto == BE16(ETH_P_IP)) {
-		if (unlikely(pktdata + sizeof(struct iphdr) > data_end))
-			DO_RETURN(PKT_LEN_DROP, XDP_DROP);
-		ip = (struct iphdr*) pktdata;
+		CHECK_LEN(pktdata, iphdr);
+		const struct iphdr *ip = (struct iphdr*) pktdata;
 
 #if PARSE_IHL == PARSE
 		if (unlikely(ip->ihl < 5)) DO_RETURN(IHL_DROP, XDP_DROP);
@@ -226,35 +220,42 @@ int xdp_drop_prog(struct xdp_md *ctx)
 		l4hdr = pktdata + 5*4;
 #endif
 
-		if (ip->protocol == IP_PROTO_TCP) {
-			if (unlikely(l4hdr + sizeof(struct tcphdr) > data_end))
-				DO_RETURN(PKT_LEN_DROP, XDP_DROP);
-			tcp = (struct tcphdr*) l4hdr;
-		} else if (ip->protocol == IP_PROTO_UDP) {
-			if (unlikely(l4hdr + sizeof(struct udphdr) > data_end))
-				DO_RETURN(PKT_LEN_DROP, XDP_DROP);
-			udp = (struct udphdr*) l4hdr;
-		} else if (ip->protocol == IP_PROTO_ICMP) {
-			if (unlikely(l4hdr + sizeof(struct icmphdr) > data_end))
-				DO_RETURN(PKT_LEN_DROP, XDP_DROP);
-			icmp = (struct icmphdr*) l4hdr;
+		const struct icmphdr *icmp = NULL;
+		if ((ip->frag_off & BE16(IP_OFFSET)) == 0) {
+			if (ip->protocol == IP_PROTO_TCP) {
+				CHECK_LEN(l4hdr, tcphdr);
+				tcp = (struct tcphdr*) l4hdr;
+				sport = BE16(tcp->source);
+				dport = BE16(tcp->dest);
+				ports_valid = 1;
+			} else if (ip->protocol == IP_PROTO_UDP) {
+				CHECK_LEN(l4hdr, udphdr);
+				const struct udphdr *udp = (struct udphdr*) l4hdr;
+				sport = BE16(udp->source);
+				dport = BE16(udp->dest);
+				ports_valid = 1;
+			} else if (ip->protocol == IP_PROTO_ICMP) {
+				CHECK_LEN(l4hdr, icmphdr);
+				icmp = (struct icmphdr*) l4hdr;
+			}
 		}
+
+		RULES4
 	}
 #endif
 #ifdef NEED_V6_PARSE
 	if (eth_proto == BE16(ETH_P_IPV6)) {
-		if (unlikely(pktdata + sizeof(struct ip6hdr) > data_end))
-			DO_RETURN(PKT_LEN_DROP, XDP_DROP);
-		ip6 = (struct ip6hdr*) pktdata;
+		CHECK_LEN(pktdata, ip6hdr);
+		const struct ip6hdr *ip6 = (struct ip6hdr*) pktdata;
 
 		l4hdr = pktdata + 40;
 
 		uint8_t v6nexthdr = ip6->nexthdr;
+		const struct ip6_fraghdr *frag6 = NULL;
 #ifdef PARSE_V6_FRAG
 #if PARSE_V6_FRAG == PARSE
 		if (ip6->nexthdr == IP6_PROTO_FRAG) {
-			if (unlikely(l4hdr + sizeof(struct ip6_fraghdr) > data_end))
-				DO_RETURN(PKT_LEN_DROP, XDP_DROP);
+			CHECK_LEN(l4hdr, ip6_fraghdr);
 			frag6 = (struct ip6_fraghdr*) l4hdr;
 			l4hdr = l4hdr + sizeof(struct ip6_fraghdr);
 			v6nexthdr = frag6->nexthdr;
@@ -264,34 +265,31 @@ int xdp_drop_prog(struct xdp_md *ctx)
 #endif
 		}
 #endif
-
-		if (v6nexthdr == IP_PROTO_TCP) {
-			if (unlikely(l4hdr + sizeof(struct tcphdr) > data_end))
-				DO_RETURN(PKT_LEN_DROP, XDP_DROP);
-			tcp = (struct tcphdr*) l4hdr;
-		} else if (v6nexthdr == IP_PROTO_UDP) {
-			if (unlikely(l4hdr + sizeof(struct udphdr) > data_end))
-				DO_RETURN(PKT_LEN_DROP, XDP_DROP);
-			udp = (struct udphdr*) l4hdr;
-		} else if (v6nexthdr == IP6_PROTO_ICMPV6) {
-			if (unlikely(l4hdr + sizeof(struct icmp6hdr) > data_end))
-				DO_RETURN(PKT_LEN_DROP, XDP_DROP);
-			icmpv6 = (struct icmp6hdr*) l4hdr;
+		// TODO: Handle more options?
+
+		const struct icmp6hdr *icmpv6 = NULL;
+		if (frag6 == NULL || (frag6->frag_off & BE16(IP6_FRAGOFF)) == 0) {
+			if (v6nexthdr == IP_PROTO_TCP) {
+				CHECK_LEN(l4hdr, tcphdr);
+				tcp = (struct tcphdr*) l4hdr;
+				sport = BE16(tcp->source);
+				dport = BE16(tcp->dest);
+				ports_valid = 1;
+			} else if (v6nexthdr == IP_PROTO_UDP) {
+				CHECK_LEN(l4hdr, udphdr);
+				const struct udphdr *udp = (struct udphdr*) l4hdr;
+				sport = BE16(udp->source);
+				dport = BE16(udp->dest);
+				ports_valid = 1;
+			} else if (v6nexthdr == IP6_PROTO_ICMPV6) {
+				CHECK_LEN(l4hdr, icmp6hdr);
+				icmpv6 = (struct icmp6hdr*) l4hdr;
+			}
 		}
-		// TODO: Handle some options?
-	}
-#endif
 
-	uint16_t sport, dport; // Host Endian! Only valid with tcp || udp
-	if (tcp != NULL) {
-		sport = BE16(tcp->source);
-		dport = BE16(tcp->dest);
-	} else if (udp != NULL) {
-		sport = BE16(udp->source);
-		dport = BE16(udp->dest);
+		RULES6
 	}
-
-	RULES
+#endif
 
 	return XDP_PASS;
 }