use seperate pcap flags for tunnel.

Trying to use a l2 based expression such as
'host ether xx-xx-xx-xx-xx-xx' results in a error
as it is not a valid l3 expression (thus compilation fails)
however, in order to be able to have both l2&l3 expressions
we need to seperate out the flags and pass them seperately.

Signed-off-by: Tom Hadlaw <[email protected]>

Author: tommyp1ckles

internal/libpcap/inject.go

@@ -17,7 +17,7 @@ func InjectL2Filter(program *ebpf.ProgramSpec, filterExpr string) (err error) {
 	return injectFilter(program, filterExpr, false, false)
 }
 
-func InjectFilters(program *ebpf.ProgramSpec, filterExpr, tunnelFilterExpr string) (err error) {
+func InjectFilters(program *ebpf.ProgramSpec, filterExpr, tunnelFilterExprL2, tunnelFilterExprL3 string) (err error) {
 	if err = injectFilter(program, filterExpr, false, false); err != nil {
 		return
 	}
@@ -28,10 +28,10 @@ func InjectFilters(program *ebpf.ProgramSpec, filterExpr, tunnelFilterExpr strin
 		return injectFilter(program, "__pwru_reject_all__", true, false)
 	}
 	// Attach any tunnel filters.
-	if err := injectFilter(program, tunnelFilterExpr, false, true); err != nil {
+	if err := injectFilter(program, tunnelFilterExprL2, false, true); err != nil {
 		return fmt.Errorf("l2 tunnel filter: %w", err)
 	}
-	if err := injectFilter(program, tunnelFilterExpr, true, true); err != nil {
+	if err := injectFilter(program, tunnelFilterExprL3, true, true); err != nil {
 		return fmt.Errorf("l3 tunnel filter: %w", err)
 	}
 	return nil

internal/pwru/types.go

@@ -38,7 +38,8 @@ type Flags struct {
 	FilterTrackBpfHelpers   bool
 	FilterIfname            string
 	FilterPcap              string
-	FilterTunnelPcap        string
+	FilterTunnelPcapL2      string
+	FilterTunnelPcapL3      string
 	FilterKprobeBatch       uint
 
 	OutputTS         string
@@ -76,7 +77,8 @@ func (f *Flags) SetFlags() {
 	flag.BoolVar(&f.FilterTrackSkb, "filter-track-skb", false, "trace a packet even if it does not match given filters (e.g., after NAT or tunnel decapsulation)")
 	flag.BoolVar(&f.FilterTrackSkbByStackid, "filter-track-skb-by-stackid", false, "trace a packet even after it is kfreed (e.g., traffic going through bridge)")
 	flag.BoolVar(&f.FilterTraceTc, "filter-trace-tc", false, "trace TC bpf progs")
-	flag.StringVar(&f.FilterTunnelPcap, "filter-tunnel-pcap", "", "pcap expression for vxlan/geneve tunnel (l3)")
+	flag.StringVar(&f.FilterTunnelPcapL2, "filter-tunnel-pcap-l2", "", "pcap expression for vxlan/geneve tunnel (l2)")
+	flag.StringVar(&f.FilterTunnelPcapL3, "filter-tunnel-pcap-l3", "", "pcap expression for vxlan/geneve tunnel (l3)")
 	flag.BoolVar(&f.FilterTraceXdp, "filter-trace-xdp", false, "trace XDP bpf progs")
 	flag.BoolVar(&f.FilterTrackBpfHelpers, "filter-track-bpf-helpers", false, "trace BPF helper functions")
 	flag.StringVar(&f.FilterIfname, "filter-ifname", "", "filter skb ifname in --filter-netns (if not specified, use current netns)")

main.go

@@ -151,7 +151,9 @@ func main() {
 			continue
 		}
 		if err = libpcap.InjectFilters(program,
-			flags.FilterPcap, flags.FilterTunnelPcap); err != nil {
+			flags.FilterPcap,
+			flags.FilterTunnelPcapL2,
+			flags.FilterTunnelPcapL3); err != nil {
 			log.Fatalf("Failed to inject filter ebpf for %s: %v", name, err)
 		}
 	}