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 Posted: Wed Sep 30, 2009 1:19 am |
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Guest
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Hi
I've written a network monitoring app for linux that displays information about
ethernet frames it receives. It creates the socket as follows:
sock = socket(PF_PACKET,SOCK_RAW,htons(ETH_P_ALL))
My 1st question is , is there a simple way to get the interface name the
frame arrived on or would I have to issue an ioctl SIOCGIFCONF call
and loop through the list of interfaces comparing the MAC addresses?
My 2nd related question is - how can I specify what interface to send an
outgoing frame on when I update the code to write to the socket?
Thanks for any help.
B2003 |
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| Posted: Wed Sep 30, 2009 1:54 am |
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Guest
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On Wed, 30 Sep 2009 06:34:22 -0500
gordon at (no spam) hammy.burditt.org (Gordon Burditt) wrote:
Quote: I'm not sure you can *TELL* the interface name the frame arrived
on by looping through the list of interfaces comparing MAC addresses.
You can if it has arrived from an ethernet interface.
Quote: Localhost doesn't have a MAC address.
Lots of virtual interfaces like 'gif' don't either.
Neither do some of the packets removed from the system, then re-injected
into it (say, by a userland NATD daemon).
What about broadcast packets?
None of the above work, which is why I was hoping that there was a way
of obtaining the packets interface directly but I suspect not.
B2003 |
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| Gordon Burditt... |
| Posted: Wed Sep 30, 2009 5:34 am |
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Guest
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Quote: I've written a network monitoring app for linux that displays information about
ethernet frames it receives. It creates the socket as follows:
sock = socket(PF_PACKET,SOCK_RAW,htons(ETH_P_ALL))
My 1st question is , is there a simple way to get the interface name the
frame arrived on or would I have to issue an ioctl SIOCGIFCONF call
and loop through the list of interfaces comparing the MAC addresses?
I'm not sure you can *TELL* the interface name the frame arrived
on by looping through the list of interfaces comparing MAC addresses.
Localhost doesn't have a MAC address.
Lots of virtual interfaces like 'gif' don't either.
Neither do some of the packets removed from the system, then re-injected
into it (say, by a userland NATD daemon).
What about broadcast packets? |
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| Robert Harris... |
| Posted: Wed Sep 30, 2009 6:47 am |
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Guest
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You have to do an ioctl with a request code SIOCGIFINDEX to get the
index and an ioctl with request code SIOCGIFNAME to get the interface
name from the index.
man 7 netdevice
will tell you a fuller story.
Robert
boltar2003 at (no spam) yahoo.co.uk wrote:
Quote: Hi
I've written a network monitoring app for linux that displays information about
ethernet frames it receives. It creates the socket as follows:
sock = socket(PF_PACKET,SOCK_RAW,htons(ETH_P_ALL))
My 1st question is , is there a simple way to get the interface name the
frame arrived on or would I have to issue an ioctl SIOCGIFCONF call
and loop through the list of interfaces comparing the MAC addresses?
My 2nd related question is - how can I specify what interface to send an
outgoing frame on when I update the code to write to the socket?
Thanks for any help.
B2003
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