I'm sorry ... I hit REPLY again to Johannes personally rather than to
the list. I don't know what it is about this list server that makes
me do it ... maybe there's no Reply-To.
Here was my followup question:
---------- Forwarded message ----------
I have another question about netlink scanning. Here is what I am
doing. First, trigger a request to starts canning:
type = genl_family_get_id(nl80211);
cmd = NL80211_CMD_TRIGGER_SCAN;
flags = 0;
pid = 0;
(void) genlmsg_put(msg, pid, seqSent, type, 0, flags, cmd, 0);
int dev = if_nametoindex("wlan0");
nla_put_u32(msg, NL80211_ATTR_IFINDEX, dev);
rc = nl_send_auto_complete(sock, msg);
Wait a little while, and I get back a valid message that indicates the
scan is complete. I handle that here:
bool try_parse_scan_status(struct nl_msg *msg) {
struct genlmsghdr *genMsgHeader = (struct genlmsghdr *) nlmsg_data(header);
/* check to make sure it's the right interface. That works so
I'll leave that code out */
switch (genMsgHeader->cmd) {
case NL80211_CMD_NEW_SCAN_RESULTS:
if (debug) {
cerr << "New scan results available" << endl;
}
nl_msg_dump(msg, stdout);
trigger_fetch_scan_results();
break;
/* other stuff deleted */
}
OK so here's what happens. I get the message back indicating the scan
is complete, yay! Then I try to call my trigger_fetch_scan_results().
What that method does is sends command NL80211_CMD_GET_SCAN on that
interface, with the flag NLM_F_DUMP. Great!
The problem is, I get a message back whose genMsgHeader->cmd STILL
says "NL80211_CMD_NEW_SCAN_RESULTS." The resulting packet has good
stuff in it (the ssid, etc. info I am looking for). UNFORTUNATELY,
because of the way I wrote my code it triggers another scan, which
causes it to say "Device or resource busy" and it just loops.
So here's the question: in my NL_CB_VALID listener, how do I
distinguish the response to the NL80211_CMD_TRIGGER_SCAN (the one that
indicates scan complete) from the response to the CMD_GET_SCAN (fetch
the results) message?
--Chris
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