tcpdump mailing list archives
Re: capturing 802.11 frames with udp protocol..
From: alex medvedev <alexm () pycckue org>
Date: Wed, 16 Jul 2003 10:40:46 -0500 (CDT)
hallo, i do not think that a wireless card supplies ieee80211 header unless in monitor mode (?) [which cisco can do, but in a receive only mode]. i think it just gives the ethernet header, so you don't have to skip the ieee80211 header from eth1 when communicating normally. -alexm -- öÉÚÎØ.exe /? On Wed, 16 Jul 2003, M. Onur ERGiN wrote:
Hi; I am quite new in these and implementing an adhoc routing algorithm in user-space of linux. I can capture some packets which are send from cisco 340 wireless clients. the packets simply include data of a simple udp program. I do the following: /*********************************** int size_MAC; //size of the mac layer header (802.11 or ethernet) if(strcmp(dev,"eth1")==0) size_MAC = sizeof(struct ieee_802_11_header)+2; else size_MAC = sizeof(struct ether_header); int size_ip = sizeof(struct ip); //int size_tcp = sizeof(struct tcphdr); int size_udp = sizeof(struct udphdr); struct scanpac sp; static int i =0; printf("DEVICE: %s\n",dev); printf("FONK!%d\n",i++); if(strcmp(dev,"eth1")!=0) eptr = (struct ether_header *)(data); else ieee_802_11_hdr = (struct ieee_802_11_header *)(data+2); ip = (struct ip *)(data + size_MAC); udp = (struct udphdr *)(data + size_MAC + size_ip); payload = (u_char *)(data + size_MAC + size_ip + size_udp); **********************************/ in most of the times, I get the headers correctly (at least they seem so :) ) but can never get the payload. first, I cast the complete packet to a 802.11 header. then I cast the rest to an ip header and the rest to a udp header. but when I try to get the very last one (which is supposed to be the payload) I see nothing on the screen using printf("%s...); any ideas? regards, Onur. __________________________________ Do you Yahoo!? SBC Yahoo! DSL - Now only $29.95 per month! http://sbc.yahoo.com - This is the TCPDUMP workers list. It is archived at http://www.tcpdump.org/lists/workers/index.html To unsubscribe use mailto:tcpdump-workers-request () tcpdump org?body=unsubscribe
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Current thread:
- capturing 802.11 frames with udp protocol.. M. Onur ERGiN (Jul 16)
- Re: capturing 802.11 frames with udp protocol.. alex medvedev (Jul 16)
- Re: capturing 802.11 frames with udp protocol.. Guy Harris (Jul 16)
- Re: capturing 802.11 frames with udp protocol.. Justin Robinson (Jul 16)
- Re: capturing 802.11 frames with udp protocol.. Guy Harris (Jul 16)
- Re: capturing 802.11 frames with udp protocol.. M. Onur ERGiN (Jul 17)
- Re: capturing 802.11 frames with udp protocol.. Justin Robinson (Jul 16)
- Re: capturing 802.11 frames with udp protocol.. Peter Moody (Jul 16)