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Opened 7 years ago

Closed 7 years ago

#442 closed defect (notadefect)

First UDP datagram not received by netecho

Reported by: Jakub Jermář Owned by:
Priority: major Milestone: 0.5.0
Component: helenos/net/udp Version: mainline
Keywords: Cc:
Blocker for: Depends on:
See also:

Description

As of mainline,1474, running HelenOS in QEMU using the default ne-qe.sh script, doing the following:

/ # inetcfg create 10.0.2.15/24 net/eth2 v4a
/ # netecho -v -p 8080

and then from the host:

$ echo foo | nc -u 127.0.0.1 8080

will not do anything, i.e. netecho will not receive the first datagram and it will not echo 'foo' to its output. According to top, the system processes two interrupts from the NIC at this point. If the nc command from the host is retried, the datagram gets through and the NIC generates again two interrupts.

Note that if the gateway IP address 10.0.2.2 is pinged from HelenOS prior to issuing the nc command from the host, then the behavior is correct and netecho prints 'foo' to its output.

The problem is not reproducible e.g. in VirtualBox when the guest networking is configured in bridged mode.

Change History (2)

comment:1 Changed 7 years ago by Jakub Jermář

After some investigation, this is beginning to look as if QEMU gw (10.0.2.2) sent an ARP request for 10.0.2.15, HelenOS replied and QEMU dropped the UDP datagram (i.e. no retransmit after ARP request).

comment:2 Changed 7 years ago by Jakub Jermář

Resolution: notadefect
Status: newclosed

The problem is not reproducible with QEMU 1.0.1, but it is reproducible with e.g. QEMU 0.15.0. Closing as not a defect.

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