Add support of listening to multiple netns (#418)

* multiple netns listen - initial commit

* multiple netns listen - actual work

* remove redundant log line

* map /proc of host to tapper

* changing kubernetes provider again after big conflict

* revert node-sass version back to 5.0.0

* Rename host_source to hostSource

Co-authored-by: gadotroee <55343099+gadotroee@users.noreply.github.com>

* PR fixes - adding comment + typos + naming conventions

* go fmt + making procfs read only

* setns back to the original value after packet source initialized

Co-authored-by: gadotroee <55343099+gadotroee@users.noreply.github.com>

tap/source/packet_source_manager.go

@@ -0,0 +1,154 @@
+package source
+
+import (
+	"fmt"
+	"runtime"
+	"strconv"
+	"strings"
+
+	"github.com/up9inc/mizu/shared/logger"
+	"github.com/vishvananda/netns"
+)
+
+type PacketSourceManager struct {
+	sources []*tcpPacketSource
+}
+
+func NewPacketSourceManager(procfs string, pids string, filename string, interfaceName string,
+	behaviour TcpPacketSourceBehaviour) (*PacketSourceManager, error) {
+	sources := make([]*tcpPacketSource, 0)
+	hostSource, err := newHostPacketSource(filename, interfaceName, behaviour)
+
+	if err != nil {
+		return nil, err
+	}
+
+	sources = append(sources, hostSource)
+
+	if pids != "" {
+		netnsSources := newNetnsPacketSources(procfs, pids, interfaceName, behaviour)
+		sources = append(sources, netnsSources...)
+	}
+
+	return &PacketSourceManager{
+		sources: sources,
+	}, nil
+}
+
+func newHostPacketSource(filename string, interfaceName string,
+	behaviour TcpPacketSourceBehaviour) (*tcpPacketSource, error) {
+	var name string
+
+	if filename == "" {
+		name = fmt.Sprintf("host-%v", interfaceName)
+	} else {
+		name = fmt.Sprintf("file-%v", filename)
+	}
+
+	source, err := newTcpPacketSource(name, filename, interfaceName, behaviour)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return source, nil
+}
+
+func newNetnsPacketSources(procfs string, pids string, interfaceName string,
+	behaviour TcpPacketSourceBehaviour) []*tcpPacketSource {
+	result := make([]*tcpPacketSource, 0)
+
+	for _, pidstr := range strings.Split(pids, ",") {
+		pid, err := strconv.Atoi(pidstr)
+
+		if err != nil {
+			logger.Log.Errorf("Invalid PID: %v - %v", pid, err)
+			continue
+		}
+
+		nsh, err := netns.GetFromPath(fmt.Sprintf("%v/%v/ns/net", procfs, pid))
+
+		if err != nil {
+			logger.Log.Errorf("Unable to get netns of pid %v - %v", pid, err)
+			continue
+		}
+
+		src, err := newNetnsPacketSource(pid, nsh, interfaceName, behaviour)
+
+		if err != nil {
+			logger.Log.Errorf("Error starting netns packet source for %v - %v", pid, err)
+			continue
+		}
+
+		result = append(result, src)
+	}
+
+	return result
+}
+
+func newNetnsPacketSource(pid int, nsh netns.NsHandle, interfaceName string,
+	behaviour TcpPacketSourceBehaviour) (*tcpPacketSource, error) {
+
+	done := make(chan *tcpPacketSource)
+	errors := make(chan error)
+
+	go func(done chan<- *tcpPacketSource) {
+		// Setting a netns should be done from a dedicated OS thread.
+		//
+		// goroutines are not really OS threads, we try to mimic the issue by
+		//	locking the OS thread to this goroutine
+		//
+		runtime.LockOSThread()
+		defer runtime.UnlockOSThread()
+		
+		oldnetns, err := netns.Get()
+		
+		if err != nil {
+			logger.Log.Errorf("Unable to get netns of current thread %v", err)
+			errors <- err
+			return
+		}
+
+		if err := netns.Set(nsh); err != nil {
+			logger.Log.Errorf("Unable to set netns of pid %v - %v", pid, err)
+			errors <- err
+			return
+		}
+
+		name := fmt.Sprintf("netns-%v-%v", pid, interfaceName)
+		src, err := newTcpPacketSource(name, "", interfaceName, behaviour)
+
+		if err != nil {
+			logger.Log.Errorf("Error listening to PID %v - %v", pid, err)
+			errors <- err
+			return
+		}
+
+		if err := netns.Set(oldnetns); err != nil {
+			logger.Log.Errorf("Unable to set back netns of current thread %v", err)
+			errors <- err
+			return
+		}
+
+		done <- src
+	}(done)
+
+	select {
+	case err := <-errors:
+		return nil, err
+	case source := <-done:
+		return source, nil
+	}
+}
+
+func (m *PacketSourceManager) ReadPackets(ipdefrag bool, packets chan<- TcpPacketInfo) {
+	for _, src := range m.sources {
+		go src.readPackets(ipdefrag, packets)
+	}
+}
+
+func (m *PacketSourceManager) Close() {
+	for _, src := range m.sources {
+		src.close()
+	}
+}