[nzlug] Virtualization + ethernet/ping issues.

[Greg Fawcett]

Interesting - EAGAIN is not a serious error in itself, in that it indicates
that recvmsg() was called but no data was available. However, usually you
would only call recvmsg() when signalled, so this suggests that VMWare (I
have absolutely no knowledge of VMWare, but I assume it abstracts the
hardware) received a message, raised a signal and then had no data to
provide when recvmsg() arrived. Maybe one of the other VMWare processes
grabbed it instead?

Greg Fawcett

On 13/02/2008, Michael Hutchinson <mhutchinson at manux.co.nz> wrote:
>
> Ok, I did the strace on the PID of the ping process I'm using that is
> failing against our monitored site... I can see a definite error, but
> it's not clear what is causing it, and I'm no programmer, so half the
> discussions I find with google don't make sense to me, and they seem
> unrelated for the most part anyway.
>
> Here goes my strace: obfuscation of client IP only (XX)
>
> gettimeofday({1202864466, 216269}, NULL) = 0
> gettimeofday({1202864466, 216412}, NULL) = 0
> sendmsg(3, {msg_name(16)={sa_family=AF_INET, sin_port=htons(0),
> sin_addr=inet_addr("192.168.51.XX")},
> msg_iov(1)=[{"\10\0\223\5\nP\v\321RA\262G\\M\3\0\10\t\n\v\f\r\16\17\20".
> .., 64}], msg_controllen=0, msg_flags=0}, 0) = 64
> recvmsg(3, 0xbfffeb40, 0)               = -1 EAGAIN (Resource
> temporarily unavailable)
> gettimeofday({1202864467, 216392}, NULL) = 0
> gettimeofday({1202864467, 216524}, NULL) = 0
> sendmsg(3, {msg_name(16)={sa_family=AF_INET, sin_port=htons(0),
> sin_addr=inet_addr("192.168.51.XX")},
> msg_iov(1)=[{"\10\0\"\4\nP\v\322SA\262G\314M\3\0\10\t\n\v\f\r\16\17\20".
> .., 64}], msg_controllen=0, msg_flags=0}, 0) = 64
> recvmsg(3, 0xbfffeb40, 0)               = -1 EAGAIN (Resource
> temporarily unavailable)
>
> This should amount to two ping packets leaving and two returning.
> Tcpdump definitely see's the returning packet, but in strace I see this
> unfamiliar "-1 EAGAIN" message.
>
> I have checked our swap space, amount of physical memory available, and
> disk space. None of which are running out. The CPU is rather idle most
> of the time on this box.
>
> Anyone know what the next step ought to be?
>
> Cheers,
> Mike
>
>
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