Hi, Guibin, Your example with SO_LINGER is not relevant as this is the SO_LINGER option and not the generic IP_OPTION. Please take a look at the ping implementation: http://www.linux-ipv6.org/gitweb/gitweb.cgi?p=gitroot/iputils.git;a=blob;f=p... You have there: if (options & F_TIMESTAMP) { 492 memset(rspace, 0, sizeof(rspace)); 493 rspace[0] = IPOPT_TIMESTAMP; 494 rspace[1] = (ts_type==IPOPT_TS_TSONLY ? 40 : 36); 495 rspace[2] = 5; So for the type, byte 0, you have IPOPT_TIMESTAMP and for the length, you have 40 or 36 (It depends on ts_type) Best Regards, Rami Rosen http://ramirose.wix.com/ramirosen On Sat, Dec 14, 2013 at 3:00 AM, Guibin(Bill) Tian <gbtian@gmail.com> wrote:
Hi, maybe it's a naive question. But I am confused here.
For the options field of an IP header, as for the data in this field, according to document and the code in the method of "ip_options_compile", the first byte is the options type data and the second byte is the length of the option. But I traced back the method of "ip_options_get_from_user", there is no place that assign these two values to the __data field.
I checked some example of socket API "setsockopt", it also just converts the target options data pointer into a char * pointer and passes down to "ip_options_get_from_user", still it doesn't set these two values.
Can anyone help me on this? Because I am trying to add my own options to IP header at the IP layer for some experiment purposes.
struct linger linger = { 0 }; linger.l_onoff = 1; linger.l_linger = 30; status = setsockopt(serverSocket, SOL_SOCKET, SO_LINGER, (const char *) &linger, sizeof(linger));
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