Implement tap/tun device in vfs.

PiperOrigin-RevId: 296526279

2 files changed, 71 insertions, 0 deletions

diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index 862954ab2..46d3a6646 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -298,6 +298,33 @@ func (n *NIC) enable() *tcpip.Error {
 	return nil
 }
 
+// remove detaches NIC from the link endpoint, and marks existing referenced
+// network endpoints expired. This guarantees no packets between this NIC and
+// the network stack.
+func (n *NIC) remove() *tcpip.Error {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+
+	// Detach from link endpoint, so no packet comes in.
+	n.linkEP.Attach(nil)
+
+	// Remove permanent and permanentTentative addresses, so no packet goes out.
+	var errs []*tcpip.Error
+	for nid, ref := range n.mu.endpoints {
+		switch ref.getKind() {
+		case permanentTentative, permanent:
+			if err := n.removePermanentAddressLocked(nid.LocalAddress); err != nil {
+				errs = append(errs, err)
+			}
+		}
+	}
+	if len(errs) > 0 {
+		return errs[0]
+	}
+
+	return nil
+}
+
 // becomeIPv6Router transitions n into an IPv6 router.
 //
 // When transitioning into an IPv6 router, host-only state (NDP discovered
@@ -1302,6 +1329,11 @@ func (n *NIC) Stack() *Stack {
 	return n.stack
 }
 
+// LinkEndpoint returns the link endpoint of n.
+func (n *NIC) LinkEndpoint() LinkEndpoint {
+	return n.linkEP
+}
+
 // isAddrTentative returns true if addr is tentative on n.
 //
 // Note that if addr is not associated with n, then this function will return
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index f0ed76fbe..900dd46c5 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -916,6 +916,18 @@ func (s *Stack) CreateNIC(id tcpip.NICID, ep LinkEndpoint) *tcpip.Error {
 	return s.CreateNICWithOptions(id, ep, NICOptions{})
 }
 
+// GetNICByName gets the NIC specified by name.
+func (s *Stack) GetNICByName(name string) (*NIC, bool) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	for _, nic := range s.nics {
+		if nic.Name() == name {
+			return nic, true
+		}
+	}
+	return nil, false
+}
+
 // EnableNIC enables the given NIC so that the link-layer endpoint can start
 // delivering packets to it.
 func (s *Stack) EnableNIC(id tcpip.NICID) *tcpip.Error {
@@ -956,6 +968,33 @@ func (s *Stack) CheckNIC(id tcpip.NICID) bool {
 	return nic.enabled()
 }
 
+// RemoveNIC removes NIC and all related routes from the network stack.
+func (s *Stack) RemoveNIC(id tcpip.NICID) *tcpip.Error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	nic, ok := s.nics[id]
+	if !ok {
+		return tcpip.ErrUnknownNICID
+	}
+	delete(s.nics, id)
+
+	// Remove routes in-place. n tracks the number of routes written.
+	n := 0
+	for i, r := range s.routeTable {
+		if r.NIC != id {
+			// Keep this route.
+			if i > n {
+				s.routeTable[n] = r
+			}
+			n++
+		}
+	}
+	s.routeTable = s.routeTable[:n]
+
+	return nic.remove()
+}
+
 // NICAddressRanges returns a map of NICIDs to their associated subnets.
 func (s *Stack) NICAddressRanges() map[tcpip.NICID][]tcpip.Subnet {
 	s.mu.RLock()