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#include <camellia/syscalls.h>
#include <stdbool.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__)
handle_t eth_h;
// TODO dynamically get mac
uint8_t my_mac[] = {0x52, 0x54, 0x00, 0xCA, 0x77, 0x1A};
uint32_t my_ip = (192 << 24) + (168 << 16) + 11;
static void hexdump(const void *vbuf, size_t len) {
const 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 nput16(void *vbuf, uint16_t n) {
uint8_t *b = vbuf;
b[0] = n >> 8;
b[1] = n >> 0;
}
static void nput32(void *vbuf, uint32_t n) {
uint8_t *b = vbuf;
b[0] = n >> 24;
b[1] = n >> 16;
b[2] = n >> 8;
b[3] = n >> 0;
}
static uint16_t nget16(const void *vbuf) {
const uint8_t *b = vbuf;
return (b[0] << 8)
| (b[1] << 0);
}
static uint32_t nget32(const void *vbuf) {
const uint8_t *b = vbuf;
return (b[0] << 24)
| (b[1] << 16)
| (b[2] << 8)
| (b[3] << 0);
}
static void parse_icmp(const uint8_t *buf, size_t len) {
if (len < 4) return;
uint8_t type = buf[0];
printf("ICMP type %u\n", type);
}
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 = nget16(buf + 2);
id = nget16(buf + 4);
proto = buf[9];
src = nget32(buf + 12);
dest = nget32(buf + 16);
// 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;
}
}
static void parse_arp(const uint8_t *buf, size_t len) {
// TODO no bound checks
uint16_t htype = nget16(buf + 0);
uint16_t ptype = nget16(buf + 2);
uint16_t op = nget16(buf + 6);
const char *ops = "bad operation";
if (op == 1) ops = "request";
if (op == 2) ops = "reply";
printf("ARP htype 0x%x, ptype 0x%x, %s\n", htype, ptype, ops);
if (!(htype == 1 && ptype == 0x800)) return;
/* IPv4 over Ethernet */
if (op != 1) return;
/* a request */
uint32_t daddr = nget32(buf + 24);
printf("IPv4 request for %08x\n", daddr);
if (daddr == my_ip) {/* send a response */
char res[64];
memset(res, 0, 64);
/* Ethernet */
memcpy(res + 0, buf + 8, 6); /* from ARP sender MAC */
memcpy(res + 6, my_mac, 6);
nput16(res + 12, 0x0806); /* ethertype == ARP */
/* ARP */
nput16(res + 14, 1); /* Ethernet */
nput16(res + 16, 0x800); /* IPv4 */
res[18] = 6; res[19] = 4; /* address lengths */
nput16(res + 20, 2); /* operation == reply */
memcpy(res + 22, my_mac, 6);
nput32(res + 28, my_ip);
memcpy(res + 32, buf + 8, 10); /* sender's MAC and IP */
printf("sending ARP response:\n");
hexdump(res, sizeof res);
_syscall_write(eth_h, res, sizeof res, 0, 0);
}
}
/* 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]) {
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]);
if (false) {
/* 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 = nget16(buf + 12);
printf("ethertype %u\n", ethertype);
switch (ethertype) {
case 0x800:
parse_ipv4(buf + 14, len - 14);
break;
case 0x806:
parse_arp(buf + 14, len - 14);
break;
default:
printf("(unknown)\n");
break;
}
}
int main(void) {
const char *path = "/kdev/eth";
eth_h = _syscall_open(path, strlen(path), 0);
if (eth_h < 0) {
eprintf("couldn't open %s", path);
return 1;
}
const size_t buflen = 4096;
char *buf = malloc(buflen);
for (;;) {
long ret = _syscall_read(eth_h, buf, buflen, -1);
if (ret < 0) break;
printf("\npacket of length %u\n", ret);
hexdump(buf, ret);
parse_ethernet((void*)buf, ret);
}
free(buf);
return 0;
}
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