Ejemplo básico de uso de raw sockets que manda un frame saludador por UDP.

diff --git a/pruebas/c/net_ethernet_packet.c b/pruebas/c/net_ethernet_packet.c
new file mode 100644 (file)
index 0000000..74cd05f
--- /dev/null
+++ b/pruebas/c/net_ethernet_packet.c
@@ -0,0 +1,69 @@
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netpacket/packet.h>
+#include <net/ethernet.h>
+#include <sys/ioctl.h>
+#include <net/if.h>
+
+int main()
+{
+       int s = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_IP));
+       struct sockaddr_ll sll;
+       struct ifreq ifr;
+       memset(&ifr, 0, sizeof(ifr));
+       strncpy(ifr.ifr_name, "eth0", sizeof(ifr));
+       if (ioctl(s, SIOCGIFINDEX, &ifr) == -1)
+       {
+               perror("ioctl()");
+               return 1;
+       }
+       memset(&sll, 0, sizeof(struct sockaddr_ll));
+       sll.sll_family = AF_PACKET;
+       sll.sll_halen = 6;
+       // Aparentemente no es necesario
+       //sll.sll_addr[0] = 0x00;
+       //sll.sll_addr[1] = 0x80;
+       //sll.sll_addr[2] = 0xc7;
+       //sll.sll_addr[3] = 0x42;
+       //sll.sll_addr[4] = 0x8d;
+       //sll.sll_addr[5] = 0x27;
+       sll.sll_ifindex = ifr.ifr_ifindex;
+       sll.sll_pkttype = PACKET_HOST; // nada de recibir broadcasts, etc.
+       unsigned char buf[] = // Mi supuesto frame
+       {
+               // Ethernet
+               0x00, 0xd0, 0x09, 0xac, 0x32, 0xe0, // MAC destino
+               0x00, 0x0c, 0x6e, 0x37, 0x19, 0xbf, // MAC origen
+               0x08, 0x00, // Type IP
+               // IP
+               0x45, // Version 4, Header length 5 (5*4 = 20)
+               0x00, // TOS
+               0x00, 0x21, // Total length 33
+               0x12, 0x34, // ID
+               0x40, 0x00, // Fragmentación: Don't Fragment / Offset 0
+               0x40, // TTL 64 (porque parece que le gusta a la gente)
+               0x11, // Protocol UDP
+               0x00, 0x82, // Checsum
+               0x0a, 0x0a, 0x0a, 0x02, // Source 10.10.10.2
+               0x0a, 0x0a, 0x0a, 0x01, // Destination 10.10.10.1
+               // UDP
+               0x81, 0x0d, // Src Port 33037
+               0x0b, 0x54, // Dst Port 2900
+               0x00, 0x0d, // Length 13
+               0x76, 0x8b, // Checksum
+               // Datos
+               0x68, 0x6f, 0x6c, 0x61, 0x00 // "hola"
+       };
+       // Trato de mandar...
+       if (sendto(s, buf, sizeof(buf), 0, (struct sockaddr*) &sll,
+                               sizeof(struct sockaddr_ll)) < 0)
+       {
+               perror("send()");
+               return 1;
+       }
+       close(s);
+       return 0;
+}
+