support add fd parallelly

[yanxuean]

create new connect for every fd request

Signed-off-by: yanxuean yan.xuean@zte.com.cn

virtletv1.0
hit a problem.
The request and response of AddFd will be mismatch when we create plenty of pod(e.g. 10).

{"log":"E0508 07:24:05.205665   10024 manager.go:220] Error when adding pod yy-8 (d6f96ee4-5290-11e8-8d7b-fa163e15c857) to CNI network: fd key mismatch in the server response\n","stream":"stderr","time":"2018-05-08T07:24:05.205934204Z"}
{"log":"nsfix reexec: pid 28438: entering the namespaces of target pid 1\n","stream":"stderr","time":"2018-05-08T07:24:05.244085618Z"}

{"log":"I0508 07:24:05.869500   10033 nettools.go:716] Opening tap interface \"tap0\" for link \"virtlet-eth0\"\n","stream":"stderr","time":"2018-05-08T07:24:05.87005565Z"}
{"log":"I0508 07:24:05.869571   10033 nettools.go:721] Adding interface \"virtlet-eth0\" as \"tap0\"\n","stream":"stderr","time":"2018-05-08T07:24:05.870131321Z"}
{"log":"2018/05/08 07:24:06 transport: http2Server.HandleStreams failed to receive the preface from client: EOF\n","stream":"stderr","time":"2018-05-08T07:24:06.092375098Z"}
{"log":"E0508 07:24:06.371938   10024 manager.go:220] Error when adding pod yy-7 (d601d1c1-5290-11e8-8d7b-fa163e15c857) to CNI network: fd key mismatch in the server response\n","stream":"stderr","time":"2018-05-08T07:24:06.372188913Z"}
{"log":"nsfix reexec: pid 28549: entering the namespaces of target pid 1\n","stream":"stderr","time":"2018-05-08T07:24:06.415327404Z"}

---

This change is 

[jellonek]

There is no more a need to do that for AddFd over a unix socket connection (finally tapmanager is now internal to virtlet process goroutine) and @ivan4th will provide shortly a PR in which this part of code will be changed.

Still unix domain sockets will be used for tapmanger<->vmwrapper communication so this fix can be relevant.

[jellonek]

Reviewed 1 of 1 files at r1.
Reviewable status: 0 of 2 LGTMs obtained

---

pkg/tapmanager/fdserver.go, line 429 at r1 (raw file):

}

func (c *FDClient) connect() (*net.UnixConn, error) {

There is no need to return there conn as it can be set in c.conn already, so in Connect there will be also no need to assign conn to c.conn and do the error checking, as whole 6 lines added to Connect can then be replaced by single return c.connect().

---

pkg/tapmanager/fdserver.go, line 443 at r1 (raw file):

// Close closes the connection to FDServer
func (c *FDClient) close(conn *net.UnixConn) error {

Above suggested change would mean that this one is unnecessary...

---

pkg/tapmanager/fdserver.go, line 453 at r1 (raw file):

func (c *FDClient) request(hdr *fdHeader, data []byte) (*fdHeader, []byte, []byte, error) {
	conn, err := c.connect()
	if err != nil {

... also combining these 2 lines...

---

pkg/tapmanager/fdserver.go, line 456 at r1 (raw file):

		return nil, nil, nil, errors.New("not connected")
	}
	defer c.close(conn)

... with there call to defer c.conn.Close()

so rest of changes in this func from c.conn to conn will also be unnecessary.

[yanxuean]

Maybe we should wait for @ivan4th 's new PR at first:)

[yanxuean]

/HOLD

[yanxuean]

There is no need to export Connect() function to user, I remove it.
We hope FDClient.request is atomic, so we can start a connect in FDClient.request by self.

[yanxuean]

@jellonek PTAL

[ivan4th]

Thanks for the PR!

Reviewable status: 1 change requests, 0 of 2 approvals obtained (waiting on @yanxuean and @ivan4th)

[ivan4th]

Reviewed 5 of 5 files at r2.
Reviewable status: 1 change requests, 0 of 2 approvals obtained (waiting on @yanxuean and @ivan4th)

[yanxuean]

@jellonek PTAL

[lukaszo]

Reviewable status: 1 change requests, 1 of 2 approvals obtained (waiting on @yanxuean)