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/* minilogd.c
*
* A pale imitation of syslogd. Most notably, doesn't write anything
* anywhere except possibly back to syslogd.
*
*/
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <syslog.h>
#include <unistd.h>
#include <sys/poll.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
static int we_own_log=0;
static char **buffer=NULL;
static int buflines=0;
int debug;
int recvsock;
void alarm_handler(int x) {
alarm(0);
close(recvsock);
recvsock = -1;
}
void freeBuffer() {
struct sockaddr_un addr;
int sock;
int x=0,conn;
bzero(&addr,sizeof(addr));
addr.sun_family = AF_LOCAL;
strncpy(addr.sun_path,_PATH_LOG,sizeof(addr.sun_path)-1);
/* wait for klogd to hit syslog */
sleep(2);
sock = socket(AF_LOCAL, SOCK_DGRAM,0);
conn=connect(sock,(struct sockaddr *) &addr,sizeof(addr));
while (x<buflines) {
if (!conn) write(sock,buffer[x],strlen(buffer[x])+1);
free(buffer[x]);
x++;
}
}
void cleanup(int exitcode) {
/* If we own the log, unlink it before trying to free our buffer.
* Otherwise, sending the buffer to /dev/log doesn't make much sense.... */
if (we_own_log) {
perror("wol");
unlink(_PATH_LOG);
}
/* Don't try to free buffer if we were called from a signal handler */
if (exitcode<=0) {
if (buffer) freeBuffer();
exit(exitcode);
} else
exit(exitcode+128);
}
void runDaemon(int sock) {
struct sockaddr_un addr;
int x,len,addrlen,done=0;
char *message;
struct stat s1,s2;
struct pollfd pfds;
daemon(0,-1);
/* try not to leave stale sockets lying around */
/* Hopefully, we won't actually get any of these */
signal(SIGHUP,cleanup);
signal(SIGINT,cleanup);
signal(SIGQUIT,cleanup);
signal(SIGILL,cleanup);
signal(SIGABRT,cleanup);
signal(SIGFPE,cleanup);
signal(SIGSEGV,cleanup);
signal(SIGPIPE,cleanup);
signal(SIGBUS,cleanup);
signal(SIGTERM,cleanup);
done = 0;
/* Get stat info on /dev/log so we can later check to make sure we
* still own it... */
if (stat(_PATH_LOG,&s1) != 0)
memset(&s1, '\0', sizeof(struct stat));
while (!done) {
pfds.fd = sock;
pfds.events = POLLIN|POLLPRI;
if ( ( (x=poll(&pfds,1,500))==-1) && errno !=EINTR) {
perror("poll");
cleanup(-1);
}
if ( (x>0) && pfds.revents & (POLLIN | POLLPRI)) {
message = calloc(8192,sizeof(char));
recvsock = accept(sock,(struct sockaddr *) &addr, &addrlen);
alarm(2);
signal(SIGALRM, alarm_handler);
len = read(recvsock,message,8192);
alarm(0);
close(recvsock);
if (len>0) {
if (buflines < 200000) {
if (buffer)
buffer = realloc(buffer,(buflines+1)*sizeof(char *));
else
buffer = malloc(sizeof(char *));
message[strlen(message)]='\n';
buffer[buflines]=message;
buflines++;
}
}
else {
recvsock=-1;
}
}
if ( (x>0) && ( pfds.revents & (POLLHUP | POLLNVAL)) )
done = 1;
/* Check to see if syslogd's yanked our socket out from under us */
if ( (stat(_PATH_LOG,&s2)!=0) ||
(s1.st_ino != s2.st_ino ) || (s1.st_ctime != s2.st_ctime) ||
(s1.st_mtime != s2.st_mtime) || (s1.st_atime != s2.st_atime) ) {
done = 1;
we_own_log = 0;
}
}
cleanup(0);
}
int main(int argc, char **argv) {
struct sockaddr_un addr;
int sock;
int pid;
/* option processing made simple... */
if (argc>1) debug=1;
/* just in case */
sock = open("/dev/null",O_RDWR);
dup2(sock,0);
dup2(sock,1);
dup2(sock,2);
bzero(&addr, sizeof(addr));
addr.sun_family = AF_LOCAL;
strncpy(addr.sun_path,_PATH_LOG,sizeof(addr.sun_path)-1);
sock = socket(AF_LOCAL, SOCK_STREAM,0);
unlink(_PATH_LOG);
/* Bind socket before forking, so we know if the server started */
if (!bind(sock,(struct sockaddr *) &addr, sizeof(addr))) {
we_own_log = 1;
listen(sock,5);
if ((pid=fork())==-1) {
perror("fork");
exit(3);
}
if (pid) {
exit(0);
} else {
runDaemon(sock);
/* shouldn't get back here... */
exit(4);
}
} else {
exit(5);
}
}
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