Support RTM_DELLINK

This change will allow us to remove the default link in a packetimpact test so
we can reduce indeterministic behaviors as required in https://fxbug.dev/78430.
This will also help with testing #1388.

Updates #578, #1388.

PiperOrigin-RevId: 387896847

1 files changed, 48 insertions, 5 deletions

diff --git a/pkg/tcpip/link/fdbased/packet_dispatchers.go b/pkg/tcpip/link/fdbased/packet_dispatchers.go
index ab2855a63..fab34c5fa 100644
--- a/pkg/tcpip/link/fdbased/packet_dispatchers.go
+++ b/pkg/tcpip/link/fdbased/packet_dispatchers.go
@@ -18,6 +18,8 @@
 package fdbased
 
 import (
+	"fmt"
+
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
@@ -114,9 +116,36 @@ func (b *iovecBuffer) pullViews(n int) buffer.VectorisedView {
 	return buffer.NewVectorisedView(n, views)
 }
 
+// stopFd is an eventfd used to signal the stop of a dispatcher.
+type stopFd struct {
+	efd int
+}
+
+func newStopFd() (stopFd, error) {
+	efd, err := unix.Eventfd(0, unix.EFD_NONBLOCK)
+	if err != nil {
+		return stopFd{efd: -1}, fmt.Errorf("failed to create eventfd: %w", err)
+	}
+	return stopFd{efd: efd}, nil
+}
+
+// stop writes to the eventfd and notifies the dispatcher to stop. It does not
+// block.
+func (s *stopFd) stop() {
+	increment := []byte{1, 0, 0, 0, 0, 0, 0, 0}
+	if n, err := unix.Write(s.efd, increment); n != len(increment) || err != nil {
+		// There are two possible errors documented in eventfd(2) for writing:
+		// 1. We are writing 8 bytes and not 0xffffffffffffff, thus no EINVAL.
+		// 2. stop is only supposed to be called once, it can't reach the limit,
+		// thus no EAGAIN.
+		panic(fmt.Sprintf("write(efd) = (%d, %s), want (%d, nil)", n, err, len(increment)))
+	}
+}
+
 // readVDispatcher uses readv() system call to read inbound packets and
 // dispatches them.
 type readVDispatcher struct {
+	stopFd
 	// fd is the file descriptor used to send and receive packets.
 	fd int
 
@@ -128,7 +157,15 @@ type readVDispatcher struct {
 }
 
 func newReadVDispatcher(fd int, e *endpoint) (linkDispatcher, error) {
-	d := &readVDispatcher{fd: fd, e: e}
+	stopFd, err := newStopFd()
+	if err != nil {
+		return nil, err
+	}
+	d := &readVDispatcher{
+		stopFd: stopFd,
+		fd:     fd,
+		e:      e,
+	}
 	skipsVnetHdr := d.e.gsoKind == stack.HWGSOSupported
 	d.buf = newIovecBuffer(BufConfig, skipsVnetHdr)
 	return d, nil
@@ -136,8 +173,8 @@ func newReadVDispatcher(fd int, e *endpoint) (linkDispatcher, error) {
 
 // dispatch reads one packet from the file descriptor and dispatches it.
 func (d *readVDispatcher) dispatch() (bool, tcpip.Error) {
-	n, err := rawfile.BlockingReadv(d.fd, d.buf.nextIovecs())
-	if n == 0 || err != nil {
+	n, err := rawfile.BlockingReadvUntilStopped(d.efd, d.fd, d.buf.nextIovecs())
+	if n <= 0 || err != nil {
 		return false, err
 	}
 
@@ -184,6 +221,7 @@ func (d *readVDispatcher) dispatch() (bool, tcpip.Error) {
 // recvMMsgDispatcher uses the recvmmsg system call to read inbound packets and
 // dispatches them.
 type recvMMsgDispatcher struct {
+	stopFd
 	// fd is the file descriptor used to send and receive packets.
 	fd int
 
@@ -207,7 +245,12 @@ const (
 )
 
 func newRecvMMsgDispatcher(fd int, e *endpoint) (linkDispatcher, error) {
+	stopFd, err := newStopFd()
+	if err != nil {
+		return nil, err
+	}
 	d := &recvMMsgDispatcher{
+		stopFd:  stopFd,
 		fd:      fd,
 		e:       e,
 		bufs:    make([]*iovecBuffer, MaxMsgsPerRecv),
@@ -235,8 +278,8 @@ func (d *recvMMsgDispatcher) dispatch() (bool, tcpip.Error) {
 		d.msgHdrs[k].Msg.SetIovlen(iovLen)
 	}
 
-	nMsgs, err := rawfile.BlockingRecvMMsg(d.fd, d.msgHdrs)
-	if err != nil {
+	nMsgs, err := rawfile.BlockingRecvMMsgUntilStopped(d.efd, d.fd, d.msgHdrs)
+	if nMsgs == -1 || err != nil {
 		return false, err
 	}
 	// Process each of received packets.