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Merge pull request #734 from jcvenegas/fix-372
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protocols: client: Add timeout for hybrid vsock handshake
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Julio Montes authored Feb 20, 2020
2 parents f399498 + 8f57eda commit d26a505
Showing 1 changed file with 34 additions and 17 deletions.
51 changes: 34 additions & 17 deletions protocols/client/client.go
Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ package client
import (
"bufio"
"context"
"errors"
"fmt"
"net"
"net/url"
Expand Down Expand Up @@ -400,6 +401,7 @@ func HybridVSockDialer(sock string, timeout time.Duration) (net.Conn, error) {
}

dialFunc := func() (net.Conn, error) {
handshakeTimeout := 10 * time.Second
conn, err := net.DialTimeout("unix", udsPath, timeout)
if err != nil {
return nil, err
Expand All @@ -418,26 +420,41 @@ func HybridVSockDialer(sock string, timeout time.Duration) (net.Conn, error) {
return nil, err
}

// A trivial handshake is included in the host-initiated vsock connection protocol.
// It looks like this:
// - [host] CONNECT <port><LF>
// - [guest/success] OK <assigned_host_port><LF>
reader := bufio.NewReader(conn)
response, err := reader.ReadString('\n')
if err != nil {
conn.Close()
agentClientLog.WithField("Error", err).Debug("HybridVsock trivial handshake failed")
// for now, we temporarily rely on the backoff strategy from GRPC for more stable CI.
errChan := make(chan error)

go func() {
reader := bufio.NewReader(conn)
response, err := reader.ReadString('\n')
if err != nil {
errChan <- err
return
}

agentClientLog.WithField("response", response).Debug("HybridVsock trivial handshake")

if strings.Contains(response, "OK") {
errChan <- nil
} else {
errChan <- errors.New("HybridVsock trivial handshake failed with malformed response code")
}
}()

select {
case err = <-errChan:
if err != nil {
conn.Close()
agentClientLog.WithField("Error", err).Debug("HybridVsock trivial handshake failed")
return nil, err

}
return conn, nil
} else if !strings.Contains(response, "OK") {
case <-time.After(handshakeTimeout):
// Timeout: kernel vsock implementation has a race condition, where no response is given
// Instead of waiting forever for a response, timeout after a fair amount of time.
// See: https://lore.kernel.org/netdev/[email protected]/
conn.Close()
agentClientLog.WithField("response", response).Debug("HybridVsock trivial handshake failed with malformd response code")
// for now, we temporarily rely on the backoff strategy from GRPC for more stable CI.
return conn, nil
return nil, errors.New("timeout waiting for hybrid vsocket handshake")
}
agentClientLog.WithField("response", response).Debug("HybridVsock trivial handshake")

return conn, nil
}

timeoutErr := grpcStatus.Errorf(codes.DeadlineExceeded, "timed out connecting to hybrid vsocket %s", sock)
Expand Down

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