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Copyright (c) 2017 grugrut.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <>.
#include <emacs-module.h>
#include <pcap.h>
#include <stdio.h>
#include <stdlib.h>
int plugin_is_GPL_compatible;
struct bpf_program fp;
char filter_exp[] = "";
bpf_u_int32 mask;
bpf_u_int32 net;
struct sniff_ethernet {
u_char ether_dhost[6];
u_char ether_shost[6];
u_short ether_type;
struct sniff_ip {
u_char ip_vhl;
u_char ip_tos;
u_short ip_len;
u_short ip_id;
u_short ip_off;
u_char ip_tol;
u_char ip_protocol;
u_short ip_chksum;
u_char ip_src[4];
u_char ip_dst[4];
#define SIZE_ETHERNET 14
static emacs_value
Femacshark_init(emacs_env *env, ptrdiff_t nargs, emacs_value args[], void *data)
char *dev, errbuf[PCAP_ERRBUF_SIZE];
dev = pcap_lookupdev(errbuf);
if (dev == NULL) {
fprintf(stderr, "Could'nt find device: %s\n", errbuf);
return env->intern(env, "nil");
printf("Device:%s\n", dev);
pcap_t *handle = pcap_open_live(dev, BUFSIZ, 1, 1000, errbuf);
if (handle == NULL) {
fprintf(stderr, "Couldn't open device: %s: %s\n", dev, errbuf);
return env->intern(env, "nil");
if (pcap_compile(handle, &fp, filter_exp, 0, net) == -1) {
fprintf(stderr, "Couldn't parse filter %s: %s", filter_exp, pcap_geterr(handle));
return env->intern(env, "nil");
if (pcap_setfilter(handle, &fp) == -1) {
fprintf(stderr, "Couldn't install filter %s: %s", filter_exp, pcap_geterr(handle));
return env->intern(env, "nil");
return env->make_user_ptr(env, free, handle);
static emacs_value
Femacshark_get (emacs_env *env, ptrdiff_t nargs, emacs_value args[], void *data)
struct pcap_pkthdr header;
const u_char *packet;
const struct sniff_ip *ip;
pcap_t *handle = env->get_user_ptr(env, args[0]);
if (env->non_local_exit_check(env) != emacs_funcall_exit_return) {
return env->intern(env, "nil");
packet = pcap_next(handle, &header);
if (header.len == 0) {
return env->intern(env, "nil");
ip = (struct sniff_ip*)(packet + SIZE_ETHERNET);
char str[40];
int len = sprintf(str, "%d.%d.%d.%d -> %d.%d.%d.%d",
(ip)->ip_src[0], (ip)->ip_src[1],(ip)->ip_src[2],(ip)->ip_src[3],
(ip)->ip_dst[0], (ip)->ip_dst[1],(ip)->ip_dst[2],(ip)->ip_dst[3]);
return env->make_string(env, str, len);
static emacs_value
Femacshark_close (emacs_env *env, ptrdiff_t nargs, emacs_value args[], void *data)
pcap_t *handle = env->get_user_ptr(env, args[0]);
return env->intern(env, "t");
/* Provide FEATURE to Emacs. */
static void
provide (emacs_env *env, const char *feature)
/* call 'provide' with FEATURE converted to a symbol */
emacs_value Qfeat = env->intern (env, feature);
emacs_value Qprovide = env->intern (env, "provide");
emacs_value args[] = { Qfeat };
env->funcall (env, Qprovide, 1, args);
/* Bind NAME to FUN. */
static void
bind_function (emacs_env *env, const char *name, emacs_value Sfun)
/* Set the function cell of the symbol named NAME to SFUN using
the 'fset' function. */
/* Convert the strings to symbols by interning them */
emacs_value Qfset = env->intern (env, "fset");
emacs_value Qsym = env->intern (env, name);
/* Prepare the arguments array */
emacs_value args[] = { Qsym, Sfun };
/* Make the call (2 == nb of arguments) */
env->funcall (env, Qfset, 2, args);
emacs_module_init (struct emacs_runtime *ert)
emacs_env *env = ert->get_environment (ert);
#define DEFUN(lsym, csym, amin, amax, doc, data) \
bind_function (env, lsym, \
env->make_function(env, amin, amax, csym, doc, data))
DEFUN ("emacshark-init", Femacshark_init, 0, 0, "Init emacshark", NULL);
DEFUN ("emacshark-get", Femacshark_get, 1, 1, "Get next packet", NULL);
DEFUN ("emacshark-close", Femacshark_close, 1, 1, "Close emacshark", NULL);
#undef DEFUN
provide (env, "emacshark");
/* loaded successfully */
return 0;