From mboxrd@z Thu Jan 1 00:00:00 1970 From: "J." Subject: Re: Creating a routing program - the basics Date: Fri, 2 Nov 2007 19:28:38 +0100 (CET) Message-ID: References: Reply-To: "J." Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-c-programming-owner@vger.kernel.org List-Id: Content-Type: TEXT/PLAIN; charset="utf-8" To: linux-c-programming@vger.kernel.org Cc: Mateus Interciso On Tue, 23 Oct 2007, Mateus Interciso wrote: > On Tue, 23 Oct 2007 15:56:22 +0200, Steve Graegert wrote: >=20 > > On 10/23/07, Mateus Interciso wrote: > >> On Tue, 23 Oct 2007 13:15:11 +0200, Steve Graegert wrote: > >> > >> > On 10/23/07, Mateus Interciso wrote: > >> >> Hello, I'm currently on university, and for my graduation paper= , > >> >> I'll be implementing a routing algorythm, by hand, in C. The ro= uting > >> >> 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 t= hat > >> >> good in english: > >> >> > >> >> [PC with n NICs]-----(n cables)---->[n PCs] > >> >> > >> >> I have full control of the first PC, of course, since is the on= e 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 star= t > >> >> sending packets? > >> > > >> > Probably this is a starting point: (not tested) > >> > > >> > ___ BEGIN SOURCE ___ > >> > > >> > #include > >> > #include > >> > #include > >> > #include > >> > > >> > int read_mac(void) { > >> > int sock, sockfd, n, cnt; > >> > char buffer[2048]; > >> > unsigned char *iphead, *ethhead; > >> > struct ether_addr ether; > >> > > >> > if ((sock =3D socket(PF_PACKET, SOCK_RAW, htons(ETH_P_IP))= ) < 0) > >> > { > >> > perror("socket"); > >> > exit(1); > >> > } > >> > > >> > while (1) { > >> > if ((n =3D recvfrom(sock, buffer, 2048, 0, NULL, N= ULL)) > >> > =3D=3D > >> -1) { > >> > perror("recvfrom"); > >> > close(sock); > >> > exit(1); > >> > } > >> > > >> > ethhead =3D (unsigned char *)buffer; > >> > > >> > if (ethhead !=3D NULL) { > >> > iphead =3D (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[1= 1]); > >> > > >> > if (*iphead =3D=3D 0x45) { // Check for IP= v4, 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 =3D 11): %02= x > >> > 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 net= work > >> > programming. Otherwise you'll be asking a lot of theses questio= ns in > >> > the future. Anyway, hope this helps. > >> > > >> > \Steve > >> > > >> > -- > >> > > >> > Steve Gr=C3=A4gert > >> > DigitalEther.de > >> > - > >> > To unsubscribe from this list: send the line "unsubscribe > >> > linux-c-programming" in the body of a message to > >> > majordomo@vger.kernel.org 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? > >=20 > > I can't make any recommendations beyond the well-known programming = books > > like Steven's UNP and O'Reilly's "Understanding the Linux Kernel".=20 > > Additionally, you may find Sams Publishing 's "Linux(R) Socket > > Programming" (0672319357) useful. > >=20 > > \Steve > >=20 > > -- > >=20 > > Steve Gr=C3=A4gert > > DigitalEther.de > > - > > To unsubscribe from this list: send the line "unsubscribe > > linux-c-programming" in the body of a message to > > majordomo@vger.kernel.org More majordomo info at=20 > > http://vger.kernel.org/majordomo-info.html >=20 > Thank you, I'll take a look at those books :D >=20 > Mateus Hi, I would most certainly in the first place go for the following books by= Richard Stevens: # TCP/IP Illustrated, Volume 1: The Protocols, Addison-Wesley, 1994. # TCP/IP Illustrated, Volume 2: The Implementation, Addison-Wesley, 199= 5. # TCP/IP Illustrated, Volume 3: TCP for Transactions, HTTP, NNTP, and t= he UNIX Domain Protocols, Addison-Wesley, 1996. # UNIX Network Programming, Volume 1, Second Edition: Networking APIs: = Sockets and XTI, Prentice Hall, 1998. # UNIX Network Programming, Volume 2, Second Edition: Interprocess Comm= unications, Prentice Hall, 1999. for a complete list of Richard Steven's books: http://www.kohala.com/start/#books or amazon...=20 Than the source-code of libpcap [tcpdump] is always very helpful. Maybe also another suggestion; Effective TCP/IP programming by Snader [addison wesley] But the R.Stevens books are definitely the way to go if starting out wi= th C topics like you've describe above. GoodLuck. J. - To unsubscribe from this list: send the line "unsubscribe linux-c-progr= amming" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html