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inject.c
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inject.c
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#include <stdio.h>
#include <dlfcn.h>
#include <stdlib.h>
#include <signal.h>
#include <sysexits.h>
#include <sys/socket.h>
#include <netstack.h>
#define premain __attribute__((constructor)) premain
void premain(int, char *[]);
void segvhandler(int);
void postexit(void);
struct netstack instance;
void premain(int argc, char *argv[]) {
// Register error/exit handlers
signal(SIGSEGV, segvhandler);
atexit(postexit);
// TODO: Parse config based on argv/configuration file
// Initialise the netstack instance
netstack_init(&instance);
LOG(LINFO, "netstack v%s loaded, via libnshook", NETSTACK_VERSION);
}
/*!
* Runs at the event of a SIGSEGV, then raises another SIGSEGV
* @param num signal value. Set to 11 for SIGSEGV
*/
void segvhandler(int num) {
LOG(LINFO, "netstack exiting");
netstack_cleanup(&instance);
// Unbind this/all SIGSEGV handlers to prevent infinite loop
signal(SIGSEGV, SIG_DFL);
// Re-trigger the segfault
raise(num);
}
/*!
* Runs after the process exits successfully
*/
void postexit(void) {
LOG(LINFO, "netstack exiting");
netstack_cleanup(&instance);
}