networking - How to determine (using C API) the system's default NIC? -

-

in linux, after establishing dhcp lease, when run command route, last line gives me system's default route , nic.

e.g.,

kernel ip routing table destination    gateway         genmask        flags metric ref   use iface 142.157.138.0  *               255.255.254.0  u     2      0       0 wlan0 link-local     *               255.255.0.0    u     1000   0       0 wlan0 default        142.157.138.1   0.0.0.0        ug    0      0       0 wlan0

is there way nic marked "default" through c api, instead of running route , parsing output?

thanks.

(interesting in linux , darwin, windows.)

i don't know off-hand, study source. on ubuntu box, route provided net-tools:

~$ route /sbin/route ~$ dpkg -s /sbin/route net-tools: /sbin/route

so make directory somewhere, run apt-get source net-tools. poked source, , route.c looked place start. if there's no arguments passed route, calls route_info() given address family , options, grep that:

~/z$ grep -r route_info * lib/net-support.h:extern int route_info(const char *afname, int flags); lib/getroute.c: *960221 {1.02} bernd eckenfels:        renamed route_info getroute.c lib/getroute.c:int route_info(const char *afname, int options) netstat.c: *960204 {1.10} bernd eckenfels:        aftrans, usage, new route_info,  netstat.c:      = route_info(afname, options); route.c: *       {1.79} bernd eckenfels:        route_info route.c:    = route_info(afname, options);

great. lib/getroute.c looks promising. looks it's choosing function call based of table of function pointers, sorted address family. let's find ipv4 one:

inet_aftype.rprint = inet_rprint;

so need find definition of inet_rprint. grep delivers: it's in lib/inet_gr.c. interesting thing here fopen(_path_procnet_route, "r"), defined in lib/pathnames.h /proc/net/route. proc_gen_fmt defined in lib/proc.c used make parsing output easier.

so answer, @ least on gnu/linux box, read /proc/net/route.


Comments

Post a Comment

Popular posts from this blog

ASP.NET/SQL find the element ID and update database -

-
basically i've got update query runs when click submit button. i have asp:repeater in page layer inside this <asp:repeater id="dgbookings" runat="server" onitemdatabound="itemdb"> <itemtemplate> <div class="bookingscontent"> <div class="bookingdetails" id="<%# databinder.eval(container.dataitem, "booking_ref") %>"> <p class="infotext"><%# databinder.eval(container.dataitem, "adults") %> <asp:linkbutton onclick="editdetails" text="edit..." runat="server"></asp:linkbutton></p> <p class="infotext"><asp:linkbutton onclick="submitdetails" text="submit..." runat="server"></asp:linkbutton></p> </div> </div> </itemtemplate> <asp:repeater> and outputs ...
Read more

jquery - appear modal windows bottom -

-
i have modal windows in application, work fine <div id="modal" class="modal hide fade" tabindex="-1" role="dialog" aria-labelledby="mymodallabel" aria-hidden="true"> but when modal appears, appear top of windows, , want appear bottom the application joomla 3.0! , using template of meet gavern any idea? i found solution i modified de css in bootstrap .modal.fade { top:-25%; -webkit-transition:opacity .3s linear, bottom .3s ease-out; -moz-transition:opacity .3s linear, bottom .3s ease-out; -ms-transition:opacity .3s linear, bottom .3s ease-out; -o-transition:opacity .3s linear, bottom .3s ease-out; transition:opacity .3s linear, bottom .3s ease-out; }
Read more

c++ - Compiling static TagLib 1.6.3 libraries for Windows -

-
i having super hard time compiling , using taglib 1.6.3 in qt project. i've tried can think of. taglib claims supported through cmake i'm not having luck. furthermore, i'm confused kinds of files need qt libs! i've built *.a files, *.lib, , *.dll. understand far... believe since i'm working in windows *.lib want. no matter do, end "undefined references" taglib functions try use when try compile qt project. have tried mingw32, msys, visual studio 2008, , cross-compiling windows on linux. turning nothing. what makes less sense me if compile same taglib source qt on mac (g++ think?) works fine! somewhere in windows compilation procedures have going wrong. have been smacking face on desk 30 (on , off) hours trying figure out. since qt uses mingw must compile taglib same compiler? if compile *.lib's visual studio not compatible? are *.a libraries usable in windows? (assuming mingw) i'm still trying handle on c++ stuff, after reading coun...
Read more