Hi,
I would like to track the individual packets generated from a socket.
I need the originating socket in order to set socket specific
transmit options for a network device driver ( transmit power ). I
have tried to get the socket associated with the sk_buff that is put
into dev_hard_start_xmit. The pointer to the sock structure is null.
So i tried to use the mark field in the sk_buff structure. This is to
my surprise also not set even if i mark all packets.
I use the TUN/TAP driver to test this setup and added a printk in
function tun_net_xmit
printk("TUN TAP packet mark: %d\n", skb->mark);
I mark all packets by using the following iptable rule:
iptables -t mangle -A OUTPUT -p ip -j MARK --set-mark 3
The TUN/TAP interface is attached to a userspace socket and not to
another peer. (i just open the socket to read data and discard it).
I test operation by opening a telnet connection to an ip address in
the subnet of the TUN/TAP interface.
My suspicion is that the packet mark gets 'eaten' by qdisc, is this
correct or does iptables clean up after itself ?
Am i missing something ?
do i mark the packets correctly ?
Is it even possible to determine the originating socket at the interface level ?
Best regards,
Borgert
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