Date: Thu, 09 Feb 2006 08:01:40 -0800 From: Sam Leffler <sam@errno.com> To: Geir Egeland <geir.egeland@gmail.com> Cc: freebsd-net@freebsd.org, freebsd-questions@freebsd.org Subject: Re: IEEE 802.11 Wireless Multimedia Extension (WME) and raw sockets Message-ID: <43EB6764.7040900@errno.com> In-Reply-To: <43EB3640.8090906@gmail.com>
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Geir Egeland wrote:
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> Hash: SHA1
>
> 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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