Add -n pid:x,path:x

README.md

@@ -24,6 +24,7 @@ Usage of skbdump:
   -i, --interface string       interface to capture (default "lo")
   -a, --kaddrs string          kernel addresses to trace, e.g. "0xffffffffa0272110,0xffffffffa0272118"
   -f, --kfuncs string          kernel functions to trace, e.g. "ip_rcv,icmp_rcv"
+  -n, --netns string           netns specifier, e.g. "pid:1234", "path:/var/run/netns/foo"
   -o, --output-fields string   output fields of skb, e.g. "mark,cb"
   -w, --pcap-filename string   output pcap filename (default "skbdump.pcap")
   -s, --skb-filename string    output skb filename (default "skbdump.meta")

config.go

@@ -5,9 +5,9 @@ import (
 	"strings"
 
 	"github.com/jschwinger233/skbdump/bpf"
+	"github.com/jschwinger233/skbdump/utils"
 	flag "github.com/spf13/pflag"
-	"github.com/vishvananda/netns"
-	"golang.org/x/sys/unix"
+	"github.com/vishvananda/netlink"
 )
 
 type Config struct {
@@ -19,7 +19,8 @@ type Config struct {
 	PcapFilename  string
 	PcapFilterExp string
 
-	Netns uint32
+	*utils.Netns
+	ifindex2name map[uint32]string
 }
 
 var (
@@ -35,24 +36,34 @@ func mustInitConfig() {
 	flag.StringVarP(&outputFields, "output-fields", "o", "", "output fields of skb, e.g. \"mark,cb\"")
 	flag.StringVarP(&config.SkbFilename, "skb-filename", "s", "skbdump.meta", "output skb filename")
 	flag.StringVarP(&config.PcapFilename, "pcap-filename", "w", "skbdump.pcap", "output pcap filename")
+	var netnsSpecifier string
+	flag.StringVarP(&netnsSpecifier, "netns", "n", "", "netns specifier, e.g. \"pid:1234\", \"path:/var/run/netns/foo\"")
 	flag.Parse()
-	if outputFields != "" {
-		config.OutputFields = strings.Split(outputFields, ",")
-	}
-	config.PcapFilterExp = strings.Join(flag.Args(), " ")
 
-	ns, err := netns.Get()
-	if err != nil {
-		log.Fatalf("Failed to get netns: %+v", err)
+	var err error
+	if config.Netns, err = utils.NewNetns(netnsSpecifier); err != nil {
+		log.Fatalf("failed to parse netns: %+v", err)
 	}
-	var s unix.Stat_t
-	if err = unix.Fstat(int(ns), &s); err != nil {
+	if err = config.Netns.Do(func() (err error) {
+		config.ifindex2name = make(map[uint32]string)
+		links, err := netlink.LinkList()
+		if err != nil {
+			return err
+		}
+		for _, link := range links {
+			config.ifindex2name[uint32(link.Attrs().Index)] = link.Attrs().Name
+		}
 		return
+	}); err != nil {
+		log.Fatalf("failed to get links: %+v", err)
 	}
-	config.Netns = uint32(s.Ino)
 
-	bpfObjs, err = bpf.New()
-	if err != nil {
+	if outputFields != "" {
+		config.OutputFields = strings.Split(outputFields, ",")
+	}
+	config.PcapFilterExp = strings.Join(flag.Args(), " ")
+
+	if bpfObjs, err = bpf.New(); err != nil {
 		log.Fatalf("%+v", err)
 	}
 }

main.go

@@ -40,13 +40,13 @@ func main() {
 	if err = bpfObjs.Load(bpf.LoadOptions{
 		Filter: config.PcapFilterExp,
 		BpfConfig: bpf.BpfConfig{
-			Netns: config.Netns,
+			Netns: config.Netns.Inode,
 		},
 	}); err != nil {
 		return
 	}
 
-	targets, err := target.Parse(config.Iface, config.Kfuncs, config.Kaddrs)
+	targets, err := target.Parse(config.Netns, config.Iface, config.Kfuncs, config.Kaddrs)
 	if err != nil {
 		return
 	}

skbprint.go

@@ -36,10 +36,9 @@ func skbPrint(skb *bpf.Skbdump, linktype layers.LinkType) {
 	idx++
 	fmt.Printf("%d %016x ", idx, skb.Meta.Skb)
 
-	ifname := "unknown"
-	iface, err := net.InterfaceByIndex(int(skb.Meta.Ifindex))
-	if err == nil {
-		ifname = iface.Name
+	ifname, ok := config.ifindex2name[skb.Meta.Ifindex]
+	if !ok {
+		ifname = "unknown"
 	}
 
 	ksym, off := utils.Addr2ksym(skb.Meta.At)

target/dev/dev.go

@@ -4,43 +4,47 @@ import (
 	"net"
 
 	"github.com/jschwinger233/skbdump/bpf"
-	"github.com/pkg/errors"
+	"github.com/jschwinger233/skbdump/utils"
 	"github.com/vishvananda/netlink"
 )
 
 type Device struct {
 	Name    string
 	Ifindex int
 	Link    netlink.Link
+	Netns   *utils.Netns
 
 	delIngress func() error
 	delEgress  func() error
 }
 
-func GetDevices(iface string) (devices []*Device, err error) {
-	links := []netlink.Link{}
+func GetDevices(netns *utils.Netns, iface string) (devices []*Device, _ error) {
+	return devices, netns.Do(func() (err error) {
+		links := []netlink.Link{}
 
-	if iface == "any" {
-		if links, err = netlink.LinkList(); err != nil {
-			return nil, errors.WithStack(err)
+		if iface == "any" {
+			if links, err = netlink.LinkList(); err != nil {
+				return
+			}
+		} else {
+			link, err := netlink.LinkByName(iface)
+			if err != nil {
+				return err
+			}
+			links = append(links, link)
 		}
-	} else {
-		link, err := netlink.LinkByName(iface)
-		if err != nil {
-			return nil, errors.WithStack(err)
-		}
-		links = append(links, link)
-	}
 
-	for _, link := range links {
-		linkAttrs := link.Attrs()
-		devices = append(devices, &Device{
-			Name:    linkAttrs.Name,
-			Ifindex: linkAttrs.Index,
-			Link:    link,
-		})
-	}
-	return
+		for _, link := range links {
+			linkAttrs := link.Attrs()
+			devices = append(devices, &Device{
+				Name:    linkAttrs.Name,
+				Ifindex: linkAttrs.Index,
+				Link:    link,
+				Netns:   netns,
+			})
+		}
+		return
+	})
 }
 
 func (d *Device) IsL3Device() bool {
@@ -52,20 +56,24 @@ func (d *Device) IsLoopback() bool {
 	return d.Link.Attrs().Flags&net.FlagLoopback != 0
 }
 
-func (d *Device) Attach(objs bpf.Objects) (err error) {
-	if err = d.EnsureTcQdisc(); err != nil {
-		return
-	}
-	d.delIngress, err = d.AddIngressFilter(objs.TcIngress())
-	if err != nil {
+func (d *Device) Attach(objs bpf.Objects) error {
+	return d.Netns.Do(func() (err error) {
+		if err = d.EnsureTcQdisc(); err != nil {
+			return
+		}
+		d.delIngress, err = d.AddIngressFilter(objs.TcIngress())
+		if err != nil {
+			return
+		}
+		d.delEgress, err = d.AddEgressFilter(objs.TcEgress())
 		return
-	}
-	d.delEgress, err = d.AddEgressFilter(objs.TcEgress())
-	return
+	})
 }
 
-func (d *Device) Detach() (err error) {
-	d.delIngress()
-	d.delEgress()
-	return
+func (d *Device) Detach() error {
+	return d.Netns.Do(func() (err error) {
+		d.delIngress()
+		d.delEgress()
+		return
+	})
 }

target/target.go

@@ -5,15 +5,16 @@ import (
 	"github.com/jschwinger233/skbdump/target/dev"
 	"github.com/jschwinger233/skbdump/target/kaddr"
 	"github.com/jschwinger233/skbdump/target/kfunc"
+	"github.com/jschwinger233/skbdump/utils"
 )
 
 type Target interface {
 	Attach(bpfObjects bpf.Objects) error
 	Detach() error
 }
 
-func Parse(iface, skbfuncs string, addrs string) (targets []Target, err error) {
-	devs, err := dev.GetDevices(iface)
+func Parse(netns *utils.Netns, iface, skbfuncs string, addrs string) (targets []Target, err error) {
+	devs, err := dev.GetDevices(netns, iface)
 	if err != nil {
 		return
 	}

utils/netns.go

@@ -0,0 +1,56 @@
+package utils
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/vishvananda/netns"
+	"golang.org/x/sys/unix"
+)
+
+type Netns struct {
+	Specifier string
+
+	Inode uint32
+	ns    netns.NsHandle
+}
+
+func NewNetns(specifier string) (_ *Netns, err error) {
+	var ns netns.NsHandle
+	switch {
+	case specifier == "":
+		ns, err = netns.Get()
+	case strings.HasPrefix(specifier, "pid:"):
+		pid, err := strconv.Atoi(specifier[4:])
+		if err != nil {
+			break
+		}
+		ns, err = netns.GetFromPid(pid)
+	case strings.HasPrefix(specifier, "path:"):
+		ns, err = netns.GetFromPath(specifier[5:])
+	default:
+		err = fmt.Errorf("invalid netns specifier: %s", specifier)
+	}
+	if err != nil {
+		return
+	}
+
+	var s unix.Stat_t
+	if err = unix.Fstat(int(ns), &s); err != nil {
+		return
+	}
+	return &Netns{Specifier: specifier, ns: ns, Inode: uint32(s.Ino)}, nil
+}
+
+func (n *Netns) Do(f func() error) (err error) {
+
+	orig, err := netns.Get()
+	if err != nil {
+		return err
+	}
+	defer orig.Close()
+	netns.Set(n.ns)
+	defer netns.Set(orig)
+	return f()
+}