Geir Egeland wrote:
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Hi,
I've been playing around with WME to test various network performance,
and come across a problem that I can't quite understand.
I have an application that generates traffic with various TOS
(BACKGROUND, BEST EFFORT, VOICE, VIDEO). It uses raw sockets to transmit
the IP packets. This all works well if ip->ip_len is less than 192
bytes. If ip_>ip_len is larger than 192, the call to ieee80211_classify
(/usr/src/sys/net80211/ieee80211_output.c) will classify the packet as
"BEST EFFORT" no matter what value my application set the TOS field as.
Debugging ieee80211_classify, I see that both ip->ip_tos and ip->ip_len
are set to zero when a I send a packet with ip->ip_len larger than 192
bytes.
Sniffing the network, I can see my packets have the correct TOS and
length, but they don't get the correct WME classification.
- -------------ieee80211_output.c(iee80211_classify)------------
if (eh->ether_type == htons(ETHERTYPE_IP)) {
const struct ip *ip = (struct ip *)
(mtod(m, u_int8_t *) + sizeof (*eh));
/*
* IP frame, map the TOS field.
*/
//added by myself
printf("IP_TOS: %d, IP_LEN: %d\n",ip->ip_tos,ntohl(ip->ip_len));
//end
switch (ip->ip_tos) {
case 0x08:
case 0x20:
d_wme_ac = WME_AC_BK; /* background */
break;
case 0x28:
case 0xa0:
d_wme_ac = WME_AC_VI; /* video */
break;
case 0x30: /* voice */
case 0xe0:
case 0x88: /* XXX UPSD */
case 0xb8:
d_wme_ac = WME_AC_VO;
break;
default:
d_wme_ac = WME_AC_BE;
break;
}
- -----------------------------------------------------
When I use SOCK_DGRAM socket instead of raw, everything works fine.
I use FreeBSD 6.0-STABLE and my wireless NIC uses an atheros chipset.
Has anyone got an idea what is going on ?
I'll check but the raw socket path must not have the ip header in the
expected spot in the mbuf. Most of my testing has been done with a
modified version of netperf that slaps a TOS on the socket based on a
command line argument so only UDP and TCP (not raw) traffic.
Ideally the 802.11 layer should not be doing classification; packets
should be tagged and the 802.11 layer then does the mapping according to
the standard. Groveling around inside packets to extract stuff like
this is evil.
Sam
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