c - RAW-Sockets should ignore MTU -

-

i have small problem raw-socket. have capture packets in network modify them. have add special data, timestamps. works fine, have problem witht mtu (linux).

if of application of upper layers generates packets close mtu, can not add data. decide downsize mtu of systems. got smaller packets , possible ad data. when try sendout packets raw-socket, not working.

i found (by google, in older stackoverflow threads , in linux manpages) option ip_mtu_discover help. when use setsockopt, nothing changes.

if ((s = socket(af_packet, sock_raw, eth_p_all)) < 0) {      printf("error: not open socket\n");      return -1; }  char socket_mtu = ip_pmtudisc_dont; setsockopt(s,ipproto_ip,ip_mtu_discover,socket_mtu, 1);

maybe important. downsizing of mtu done, because when add own data, resulting packet not greater 1500 + eth-header. problem is, make raw-sockets ignore local mtu of linux-system.

  1. is ip_mtu_discover right way ignore value set in mtu?
  2. is ip_mtu_discover realy usable raw-socket?
  3. are there other ways decrement segement size of protocols on layer 3 , higher?

i read, sendto() returns emsgsize (=90) when size big. have done following test.

int k = sendto(s, frame.buffer, frame_len, 0,              (struct sockaddr*)&saddrll, sizeof(saddrll));     printf("k:%i\n", k);

after calling sendto() "k" contains "-1". if depends on packet size, shouldn't "90"??

when set size of packet send smaller mtu, works fine.... little bit strange.

any nice :-)

kind regards, andreas

ok. found solution change mtu c program.

set mtu in c programmatically

buffer.ifr_mtu = 1500;   if(!ioctl(s, siocsifmtu, &buffer)) {       printf("mtu changed\n");   }

for first moment works. it's workarround, it's not realy clean. problem coul be, if application sending packet in moment resize mtu, packet big. better ideas?

kind regards, andreas


Comments

Post a Comment

Popular posts from this blog

sql - invalid in the select list because it is not contained in either an aggregate function -

-
i can't figure out rewrite sql statement avoid error below msg 8120, level 16, state 1, line 26 column 'staffmember.staffmemberid' invalid in select list because not contained in either aggregate function or group clause. sql statment select (select [dbo].[udf_readstaffmemberbasic](sm.staffmemberid) xml path ('staffmembersummary'), root ('items'), type ), count(sm.staffmemberid) totalresults, ceiling(cast(count(sm.staffmemberid) decimal)/ @pagesize) totalpages staffmember sm inner join staffmembertoadditionalrole ar on sm.staffmemberid = ar.staffmemberid (sm.firstname '%' + @name + '%' or sm.surname '%' + @name + '%') , (@floorid null or sm.floorid = @floorid) , (@directorateid null or sm.directorateid = @directorateid) , (@additionalroleid null or ar.additionalroleid = @additionalroleid) order sm.staffmemberid offset @page * @pagesize rows fe...
Read more

Angularjs unit testing - ng-disabled not working when adding text to textarea -

-
i trying test angularjs component using karma, mocha, power-assert. have textarea , button in component, button disabled based on length of text in textarea. when run component in browser works perfectly. can't figure out how test functionality. here's bit of code. inquiryform.js function inquiryform($scope) { // plan add logic here } angular.module('myapp').component('inquiryform', { controller: inquiryform, controlleras: 'inquiryform', templateurl: 'inquiryform.html' }); inquiryform.html <div class="contact"> <div>thanks contacting us.</div> <form> <textarea ng-model="inquiryform.inquirytext" name=""></textarea> <input type="submit" value="send" ng-disabled="!inquiryform.inquirytext.length"> </form> </div> inquiryformtest.js describe('inquiry form ', () => { let $r...
Read more

How to start daemon on android by adb -

-
can me please, head swollen... i trying run daemon on android emu/device command: adb -s <device_name> shell su -c /dir/daemon <port_number> but nothink happens, , no errors! if do: adb -s <device> shell and form shell cmdline: su -c /dir/daemon <port_number> than work fine. try use shell-script , run: adb -s <device_name> shell sh su -c /dir/script.sh <port_number> and try generate script qt code port number , use: adb -s <device_name> shell sh su -c /dir/script.sh but not helped... problem if enter adb shell previous run daemon - work. problem on different device/emu/iso_image different command format not work. example: adb -s <device_name> shell su -c /dir/daemon <port_number> // work @ emu, not @ iso and vice: adb -s <device_name> shell su -c "/dir/daemon <port_number>" // work @ iso etc. everybody can answer what's matter? sorry english adb shell su -c ...
Read more