nil pointer dereference panic after network reconnect

[SijmenHuizenga]

I'm seeing a nullpointer dereference panic at this file at line 1928:

gortsplib/client.go

Lines 1909 to 1936 in c308cb3

	func (c *Client) WritePacketRTPWithNTP(medi *description.Media, pkt *rtp.Packet, ntp time.Time) error {
	byts := make([]byte, c.MaxPacketSize)
	n, err := pkt.MarshalTo(byts)
	if err != nil {
	return err
	}
	byts = byts[:n]
	select {
	case <-c.done:
	return c.closeError
	default:
	}
	cm := c.setuppedMedias[medi]
	cf := cm.formats[pkt.PayloadType]
	cf.rtcpSender.ProcessPacketRTP(pkt, ntp, cf.format.PTSEqualsDTS(pkt))
	ok := c.writer.push(func() error {
	return cf.writePacketRTPInQueue(byts)
	})
	if !ok {
	return liberrors.ErrClientWriteQueueFull{}
	}
	return nil
	}

It happens when the connection is harshly broken as a result of a network disruption.

I suspect there is some race condition caused by this line:

gortsplib/client.go

Line 915 in c308cb3

c.writer = nil

The trace is:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x10 pc=0xb4a308]

goroutine 14 [running]:
github.com/bluenviron/gortsplib/v4.(*asyncProcessor).push(...)
	/home/ascento/go/pkg/mod/github.com/bluenviron/gortsplib/v4@v4.12.1/async_processor.go:58
github.com/bluenviron/gortsplib/v4.(*Client).WritePacketRTPWithNTP(0x4000544fc8, 0x400054e0a0, 0x40007e07a0, {0x5f3a38?, 0x40008ebaa8?, 0x15253c0?})
	/home/ascento/go/pkg/mod/github.com/bluenviron/gortsplib/v4@v4.12.1/client.go:1928 +0x178

[SijmenHuizenga]

I've been trying to pinpoint the cause, and my current best guess is that this is introduced in #655

Unrelated: The work in #655 is a huge step forward of working in poor network connectivity areas. Looking forward to being able to roll it out after fixing this issue.

[aler9]

Fixed by #655