Fix map reading

client/internal/dns/forwarder/bpf_bpfeb.go

@@ -61,6 +61,7 @@ type bpfProgramSpecs struct {
 //
 // It can be passed ebpf.CollectionSpec.Assign.
 type bpfMapSpecs struct {
+	XdpIpMap   *ebpf.MapSpec `ebpf:"xdp_ip_map"`
 	XdpPortMap *ebpf.MapSpec `ebpf:"xdp_port_map"`
 }
 
@@ -83,11 +84,13 @@ func (o *bpfObjects) Close() error {
 //
 // It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
 type bpfMaps struct {
+	XdpIpMap   *ebpf.Map `ebpf:"xdp_ip_map"`
 	XdpPortMap *ebpf.Map `ebpf:"xdp_port_map"`
 }
 
 func (m *bpfMaps) Close() error {
 	return _BpfClose(
+		m.XdpIpMap,
 		m.XdpPortMap,
 	)
 }

client/internal/dns/forwarder/bpf_bpfel.go

@@ -61,6 +61,7 @@ type bpfProgramSpecs struct {
 //
 // It can be passed ebpf.CollectionSpec.Assign.
 type bpfMapSpecs struct {
+	XdpIpMap   *ebpf.MapSpec `ebpf:"xdp_ip_map"`
 	XdpPortMap *ebpf.MapSpec `ebpf:"xdp_port_map"`
 }
 
@@ -83,11 +84,13 @@ func (o *bpfObjects) Close() error {
 //
 // It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
 type bpfMaps struct {
+	XdpIpMap   *ebpf.Map `ebpf:"xdp_ip_map"`
 	XdpPortMap *ebpf.Map `ebpf:"xdp_port_map"`
 }
 
 func (m *bpfMaps) Close() error {
 	return _BpfClose(
+		m.XdpIpMap,
 		m.XdpPortMap,
 	)
 }

client/internal/dns/forwarder/src/port_fwd.c

@@ -15,6 +15,13 @@
 const __u32 map_key_dns_ip = 0;
 const __u32 map_key_dns_port = 1;
 
+struct bpf_map_def SEC("maps") xdp_ip_map = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(__u32),
+	.max_entries = 10,
+};
+
 struct bpf_map_def SEC("maps") xdp_port_map = {
 	.type = BPF_MAP_TYPE_ARRAY,
 	.key_size = sizeof(__u32),
@@ -25,32 +32,37 @@ struct bpf_map_def SEC("maps") xdp_port_map = {
 __be32 dns_ip = 0;
 __be16 dns_port = 0;
 
-bool read_port_settings() {
-    __u16 *value;
-    __be32 *ip_value;
-    value = bpf_map_lookup_elem(&xdp_port_map, &map_key_dns_port);
-    if(!value) {
-        return false;
-    }
+// 13568 is 53 in big endian
+__be16 GENERAL_DNS_PORT = 13568;
 
-    dns_port = htons(*value);
+bool read_settings() {
+    __u16 *port_value;
+    __u32 *ip_value;
 
-    ip_value = bpf_map_lookup_elem(&xdp_port_map, &map_key_dns_ip);
+    // read dns ip
+    ip_value = bpf_map_lookup_elem(&xdp_ip_map, &map_key_dns_ip);
     if(!ip_value) {
         return false;
     }
     dns_ip = htonl(*ip_value);
+
+    // read dns port
+    port_value = bpf_map_lookup_elem(&xdp_port_map, &map_key_dns_port);
+    if(!port_value) {
+        return false;
+    }
+    dns_port = htons(*port_value);
     return true;
 }
 
 SEC("xdp")
 int xdp_dns_port_fwd(struct xdp_md *ctx) {
     if(dns_port == 0) {
-        if(!read_port_settings()){
+        if(!read_settings()){
             return XDP_PASS;
         }
-        bpf_printk("dns port: %d", dns_port);
-        bpf_printk("dns ip: %d", dns_ip);
+        bpf_printk("dns port: %d", ntohs(dns_port));
+        bpf_printk("dns ip: %d", ntohl(dns_ip));
     }
 
 	void *data     = (void *)(long)ctx->data;
@@ -73,13 +85,12 @@ int xdp_dns_port_fwd(struct xdp_md *ctx) {
        return XDP_PASS;
     }
 
-    // 2130706433 = 127.0.0.1
     if (ip->daddr != dns_ip) {
         return XDP_PASS;
     }
 
     // skip non dns ports
-    if (udp->source != htons(53)){
+    if (udp->dest != GENERAL_DNS_PORT){
         return XDP_PASS;
     }
 

client/internal/dns/forwarder/traffic_forwarder.go

@@ -52,7 +52,7 @@ func (tf *TrafficForwarder) Start(ip string, dnsPort int) error {
 		_ = objs.Close()
 	}()
 
-	err = objs.XdpPortMap.Put(mapKeyDNSIP, tf.ip2int(ip))
+	err = objs.XdpIpMap.Put(mapKeyDNSIP, tf.ip2int(ip))
 	if err != nil {
 		return err
 	}