NETOBSERV-1777: Allow DNS tracking to use configurable port for tracking

bpf/configs.h

@@ -9,4 +9,5 @@ volatile const u8 enable_rtt = 0;
 volatile const u8 enable_pca = 0;
 volatile const u8 enable_dns_tracking = 0;
 volatile const u8 enable_flows_filtering = 0;
+volatile const u32 dns_port = 0;
 #endif //__CONFIGS_H__

bpf/dns_tracker.h

@@ -6,7 +6,6 @@
 #define __DNS_TRACKER_H__
 #include "utils.h"
 
-#define DNS_PORT 53
 #define DNS_QR_FLAG 0x8000
 #define UDP_MAXMSG 512
 #define EINVAL 22
@@ -67,7 +66,7 @@ static __always_inline u8 calc_dns_header_offset(pkt_info *pkt, void *data_end)
 
 static __always_inline int track_dns_packet(struct __sk_buff *skb, pkt_info *pkt) {
     void *data_end = (void *)(long)skb->data_end;
-    if (pkt->id->dst_port == DNS_PORT || pkt->id->src_port == DNS_PORT) {
+    if (pkt->id->dst_port == dns_port || pkt->id->src_port == dns_port) {
         dns_flow_id dns_req;
 
         u8 len = calc_dns_header_offset(pkt, data_end);

pkg/agent/agent.go

@@ -185,6 +185,7 @@ func FlowsAgent(cfg *Config) (*Flows, error) {
 		CacheMaxSize:     cfg.CacheMaxFlows,
 		PktDrops:         cfg.EnablePktDrops,
 		DNSTracker:       cfg.EnableDNSTracking,
+		DNSTrackerPort:   cfg.DNSTrackingPort,
 		EnableRTT:        cfg.EnableRTT,
 		EnableFlowFilter: cfg.EnableFlowFilter,
 		FilterConfig: &ebpf.FilterConfig{

pkg/agent/config.go

@@ -161,6 +161,9 @@ type Config struct {
 	EnablePktDrops bool `env:"ENABLE_PKT_DROPS" envDefault:"false"`
 	// EnableDNSTracking enable DNS tracking eBPF hook to track dns query/response flows
 	EnableDNSTracking bool `env:"ENABLE_DNS_TRACKING" envDefault:"false"`
+	// DNSTrackingPort used to define which port the DNS service is mapped to at the pod level,
+	// so we can track DNS at the pod level
+	DNSTrackingPort int `env:"DNS_TRACKING_PORT" envDefault:"53"`
 	// StaleEntriesEvictTimeout specifies the maximum duration that stale entries are kept
 	// before being deleted, default is 5 seconds.
 	StaleEntriesEvictTimeout time.Duration `env:"STALE_ENTRIES_EVICT_TIMEOUT" envDefault:"5s"`

pkg/ebpf/tracer.go

@@ -39,6 +39,8 @@ const (
 	constTraceMessages       = "trace_messages"
 	constEnableRtt           = "enable_rtt"
 	constEnableDNSTracking   = "enable_dns_tracking"
+	constDNSTrackingPort     = "dns_port"
+	dnsDefaultPort           = 53
 	constEnableFlowFiltering = "enable_flows_filtering"
 	pktDropHook              = "kfree_skb"
 	constPcaEnable           = "enable_pca"
@@ -79,12 +81,14 @@ type FlowFetcherConfig struct {
 	CacheMaxSize     int
 	PktDrops         bool
 	DNSTracker       bool
+	DNSTrackerPort   int
 	EnableRTT        bool
 	EnableFlowFilter bool
 	EnablePCA        bool
 	FilterConfig     *FilterConfig
 }
 
+// nolint:cyclop
 func NewFlowFetcher(cfg *FlowFetcherConfig) (*FlowFetcher, error) {
 	if err := rlimit.RemoveMemlock(); err != nil {
 		log.WithError(err).
@@ -110,8 +114,12 @@ func NewFlowFetcher(cfg *FlowFetcherConfig) (*FlowFetcher, error) {
 	}
 
 	enableDNSTracking := 0
+	dnsTrackerPort := dnsDefaultPort
 	if cfg.DNSTracker {
 		enableDNSTracking = 1
+		if cfg.DNSTrackerPort != 0 {
+			dnsTrackerPort = cfg.DNSTrackerPort
+		}
 	}
 
 	if enableDNSTracking == 0 {
@@ -128,6 +136,7 @@ func NewFlowFetcher(cfg *FlowFetcherConfig) (*FlowFetcher, error) {
 		constTraceMessages:       uint8(traceMsgs),
 		constEnableRtt:           uint8(enableRtt),
 		constEnableDNSTracking:   uint8(enableDNSTracking),
+		constDNSTrackingPort:     uint32(dnsTrackerPort),
 		constEnableFlowFiltering: uint8(enableFlowFiltering),
 	}); err != nil {
 		return nil, fmt.Errorf("rewriting BPF constants definition: %w", err)