daemon: Add support for CRC_DAEMON_PCAP_FILE env var

The daemon can capture all VM network traffic to a pcap file, which can
be useful to debug networking issues. This capture is currently
always enabled when --log-level debug is being used.

Because of #1881 , this means a
big pcap file is created every time the daemon is run with --log-level
debug.
Since the pcap file won't be needed most of the time, this commit adds a
dedicated CRC_DAEMON_PCAP_FILE variable which gives the path where this
data should be exported. If unset, no pcap file is created.

cmd/crc/cmd/daemon.go

@@ -8,7 +8,6 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
-	"path/filepath"
 	"regexp"
 	"syscall"
 	"time"
@@ -58,7 +57,7 @@ var daemonCmd = &cobra.Command{
 
 		virtualNetworkConfig := types.Configuration{
 			Debug:             false, // never log packets
-			CaptureFile:       captureFile(),
+			CaptureFile:       os.Getenv("CRC_DAEMON_PCAP_FILE"),
 			MTU:               4000, // Large packets slightly improve the performance. Less small packets.
 			Subnet:            "192.168.127.0/24",
 			GatewayIP:         constants.VSockGateway,
@@ -113,13 +112,6 @@ var daemonCmd = &cobra.Command{
 	},
 }
 
-func captureFile() string {
-	if !isDebugLog() {
-		return ""
-	}
-	return filepath.Join(constants.CrcBaseDir, "capture.pcap")
-}
-
 func run(configuration *types.Configuration) error {
 	vsockListener, err := vsockListener()
 	if err != nil {