Sorry for the spam but this is clearer I think,
Hi,
I have a DPDK application holding some ports, and I want to have a
virtio_user port to interface with the kernel stack, For example, I
want to use tcpdump on a virtual interface. So I understand I need to
create a netlink listener which I did. And using some print statements
I am getting a packet on the netlink port when I try to use tcpdump on
the virtual interface.
My problem is that I can't figure out how to parse the packet. For
example I expect that calling TCP dump should trigger a packet to set
a promiscuous flag, and stopping tcpdump should trigger a packet to
disable promiscuous mode.
Currently from the examples this is the attr parser I have:
static int data_attr_cb(const struct nlattr *attr, void *data)
{
const struct nlattr **tb = data;
int type = mnl_attr_get_type(attr);
/* skip unsupported attribute in user-space */
if (mnl_attr_type_valid(attr, IFLA_MAX) < 0)
return MNL_CB_OK;
switch(type) {
case IFLA_MTU:
if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0) {
perror("mnl_attr_validate");
return MNL_CB_ERROR;
}
break;
case IFLA_IFNAME:
if (mnl_attr_validate(attr, MNL_TYPE_STRING) < 0) {
perror("mnl_attr_validate");
return MNL_CB_ERROR;
}
break;
}
tb[type] = attr;
return MNL_CB_OK;
}
But this doesn't give any information. Any help on how to understand
this packet would be appreciated. I thought as there is a next
attribute and maybe nested attributes if I add the following code:
while (attr != NULL)
{
attr = mnl_attr_next(attr);
type = mnl_attr_get_type(attr);
if (type == 0)
break;
printf("type: %d\n",type);
}
I might get to the promiscuous flag (30), but I am printing like 100
of those per packet. And from what I read the payload also has
attributes. This might be a stupid question but any help on
understanding this would be appreciated.
