On Tue, 23 Oct 2007 15:56:22 +0200, Steve Graegert wrote:
> On 10/23/07, Mateus Interciso <p.zarnick@xxxxxxxxx> wrote:
>> On Tue, 23 Oct 2007 13:15:11 +0200, Steve Graegert wrote:
>>
>> > On 10/23/07, Mateus Interciso <p.zarnick@xxxxxxxxx> wrote:
>> >> Hello, I'm currently on university, and for my graduation paper,
>> >> I'll be implementing a routing algorythm, by hand, in C. The routing
>> >> algorythm itself is not easy, but one of the starting parts of it,
>> >> is to find a way of discovering the MAC that it is currently
>> >> connected to, maybe is bether if I draw, since I'm not really that
>> >> good in english:
>> >>
>> >> [PC with n NICs]-----(n cables)---->[n PCs]
>> >>
>> >> I have full control of the first PC, of course, since is the one I'm
>> >> implementing the router, so I do know the MAC of it, but how to
>> >> discover the MAC on the other end of the n lines, so I can start
>> >> sending packets?
>> >
>> > Probably this is a starting point: (not tested)
>> >
>> > ___ BEGIN SOURCE ___
>> >
>> > #include <iostream>
>> > #include <stdio.h>
>> > #include <netdb.h>
>> > #include <netinet/if_ether.h>
>> >
>> > int read_mac(void) {
>> > int sock, sockfd, n, cnt;
>> > char buffer[2048];
>> > unsigned char *iphead, *ethhead;
>> > struct ether_addr ether;
>> >
>> > if ((sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_IP))) < 0)
>> > {
>> > perror("socket");
>> > exit(1);
>> > }
>> >
>> > while (1) {
>> > if ((n = recvfrom(sock, buffer, 2048, 0, NULL, NULL))
>> > ==
>> -1) {
>> > perror("recvfrom");
>> > close(sock);
>> > exit(1);
>> > }
>> >
>> > ethhead = (unsigned char *)buffer;
>> >
>> > if (ethhead != NULL) {
>> > iphead = (unsigned char *)(buffer + 14); //
>> > Skip
>> Ethernet header
>> > printf("Peer MAC: "
>> > "%02x:%02x:%02x:%02x:%02x:%02x\n",
>> > ethhead[0], ethhead[1], ethhead[2],
>> > ethhead[3], ethhead[4], ethhead[5]);
>> > printf("Source MAC: "
>> > "%02x:%02x:%02x:%02x:%02x:%02x\n",
>> > ethhead[6], ethhead[7], ethhead[8],
>> > ethhead[9], ethhead[10], ethhead[11]);
>> >
>> > if (*iphead == 0x45) { // Check for IPv4, no
>> options present
>> > printf("Peer IP: %d.%d.%d.%d\n",
>> > iphead[12], iphead[13],
>> > iphead[14], iphead[15]);
>> > printf("Source IP: %d.%d.%d.%d\n",
>> > iphead[16], iphead[17],
>> > iphead[18], iphead[19]);
>> > printf("Protocol (UDP = 11): %02x
>> > Hex\n",
>> iphead[9]);
>> > }
>> > }
>> > }
>> >
>> > return 0;
>> > }
>> >
>> >
>> > int main(int argc, char **argv) {
>> > read_mac();
>> > return EXIT_SUCCESS;
>> > }
>> >
>> > ___ END SOURCE ___
>> >
>> > Honestly, you should make yourself acquainted with low-level network
>> > programming. Otherwise you'll be asking a lot of theses questions in
>> > the future. Anyway, hope this helps.
>> >
>> > \Steve
>> >
>> > --
>> >
>> > Steve Grägert
>> > DigitalEther.de
>> > -
>> > To unsubscribe from this list: send the line "unsubscribe
>> > linux-c-programming" in the body of a message to
>> > majordomo@xxxxxxxxxxxxxxx More majordomo info at
>> > http://vger.kernel.org/majordomo-info.html
>>
>> Thank you, this will help.
>> Do you have any book/site where I can take a deep look into how to do
>> that stuff?
>
> I can't make any recommendations beyond the well-known programming books
> like Steven's UNP and O'Reilly's "Understanding the Linux Kernel".
> Additionally, you may find Sams Publishing 's "Linux(R) Socket
> Programming" (0672319357) useful.
>
> \Steve
>
> --
>
> Steve Grägert
> DigitalEther.de
> -
> To unsubscribe from this list: send the line "unsubscribe
> linux-c-programming" in the body of a message to
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Thank you, I'll take a look at those books :D
Mateus
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