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#include <camellia/syscalls.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define eprintf(fmt, ...) fprintf(stderr, "ethdump: "fmt"\n" __VA_OPT__(,) __VA_ARGS__)
static void hexdump(void *vbuf, size_t len) {
uint8_t *buf = vbuf;
for (size_t i = 0; i < len; i += 16) {
printf("%08x ", i);
for (size_t j = i; j < i + 8 && j < len; j++)
printf("%02x ", buf[j]);
printf(" ");
for (size_t j = i + 8; j < i + 16 && j < len; j++)
printf("%02x ", buf[j]);
printf("\n");
}
}
static void parse_icmp(const uint8_t *buf, size_t len) {
if (len < 4) return;
uint8_t type = buf[0];
switch (type) {
case 8:
printf("icmp type %u - echo request\n", type);
break;
default:
printf("icmp type %u - unknown\n", type);
break;
}
}
static void parse_ipv4(const uint8_t *buf, size_t len) {
uint8_t version, headerlen, proto;
uint16_t packetlen, id, fragoffset;
uint32_t dest, src;
version = buf[0] >> 4;
if (version != 4) {
printf("bad IPv4 version %u\n", version);
return;
}
headerlen = (buf[0] & 0xf) * 4;
packetlen = (buf[2] << 8) | buf[3];
id = (buf[4] << 8) | buf[5];
proto = buf[9];
src = (buf[12] << 24)
| (buf[13] << 16)
| (buf[14] << 8)
| (buf[15] << 0);
dest = (buf[16] << 24)
| (buf[17] << 16)
| (buf[18] << 8)
| (buf[19] << 0);
// TODO checksum
// TODO fragmentation
printf("headerlen %u, packetlen %u (real %u), id %u\n", headerlen, packetlen, len, id);
printf("from %x to %x\n", src, dest);
printf("id %u\n", id);
if (packetlen < headerlen) {
printf("headerlen too big\n");
return;
}
switch (proto) {
case 1:
printf("proto %u - icmp\n", proto);
parse_icmp(buf + headerlen, packetlen - headerlen);
break;
default:
printf("proto %u - unknown\n", proto);
break;
}
}
/* https://www.w3.org/TR/PNG/#D-CRCAppendix */
uint32_t crc_table[256];
static uint32_t crc32(const uint8_t *buf, size_t len) {
if (!crc_table[1]) {
eprintf("building crc cache");
for (int i = 0; i < 256; i++) {
uint32_t c = i;
for (int j = 0; j < 8; j++)
c = ((c&1) ? 0xedb88320 : 0) ^ (c >> 1);
crc_table[i] = c;
}
}
uint32_t c = 0xFFFFFFFF;
for (size_t i = 0; i < len; i++)
c = crc_table[(c ^ buf[i]) & 0xff] ^ (c >> 8);
return ~c;
}
static void parse_ethernet(const uint8_t *buf, size_t len) {
uint8_t dmac[6], smac[6];
if (len < 60) return;
for (int i = 0; i < 6; i++) dmac[i] = buf[i];
for (int i = 0; i < 6; i++) smac[i] = buf[i + 6];
printf("from %02x:%02x:%02x:%02x:%02x:%02x\n",
smac[0], smac[1], smac[2], smac[3], smac[4], smac[5]);
printf("to %02x:%02x:%02x:%02x:%02x:%02x\n",
dmac[0], dmac[1], dmac[2], dmac[3], dmac[4], dmac[5]);
/* byte order switched on purpose */
uint32_t crc = (buf[len - 1] << 24)
| (buf[len - 2] << 16)
| (buf[len - 3] << 8)
| (buf[len - 4] << 0);
printf("fcf %x, crc %x\n", crc, crc32(buf, len - 4));
uint16_t ethertype = (buf[12] << 8) | buf[13];
if (ethertype == 0x800) {
printf("ethertype %u - IPv4\n", ethertype);
parse_ipv4(buf + 14, len - 14);
} else {
printf("ethertype %u - unknown\n", ethertype);
}
}
int main(void) {
const char *path = "/kdev/eth";
handle_t h = _syscall_open(path, strlen(path), 0);
if (h < 0) {
eprintf("couldn't open %s", path);
return 1;
}
const size_t buflen = 4096;
char *buf = malloc(buflen);
for (;;) {
long ret = _syscall_read(h, buf, buflen, -1);
if (ret < 0) break;
printf("\npacket of length %u\n", ret);
hexdump(buf, ret);
parse_ethernet((void*)buf, ret);
}
return 0;
}
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