relay.c

PPPoE在Linux上的源代码

/***********************************************************************
*
* relay.c
*
* Implementation of PPPoE relay
*
* Copyright (C) 2001 Roaring Penguin Software Inc.
*
* This program may be distributed according to the terms of the GNU
* General Public License, version 2 or (at your option) any later version.
*
* LIC: GPL
*
* $Id: relay.c,v 1.24 2002/04/09 17:28:39 dfs Exp $
*
***********************************************************************/
static char const RCSID[] =
"$Id: relay.c,v 1.24 2002/04/09 17:28:39 dfs Exp $";

#define _GNU_SOURCE 1 /* For SA_RESTART */

#include "relay.h"

#include <signal.h>

#ifdef HAVE_SYSLOG_H
#include <syslog.h>
#endif

#ifdef HAVE_GETOPT_H
#include <getopt.h>
#endif

#include <stdlib.h>
#include <string.h>
#include <errno.h>

#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif

#ifdef HAVE_SYS_UIO_H
#include <sys/uio.h>
#endif

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif


/* Interfaces (max MAX_INTERFACES) */
PPPoEInterface Interfaces[MAX_INTERFACES];
int NumInterfaces;

/* Relay info */
int NumSessions;
int MaxSessions;
PPPoESession *AllSessions;
PPPoESession *FreeSessions;
PPPoESession *ActiveSessions;

SessionHash *AllHashes;
SessionHash *FreeHashes;
SessionHash *Buckets[HASHTAB_SIZE];

volatile unsigned int Epoch = 0;
volatile unsigned int CleanCounter = 0;

/* How often to clean up stale sessions? */
#define MIN_CLEAN_PERIOD 30  /* Minimum period to run cleaner */
#define TIMEOUT_DIVISOR 20   /* How often to run cleaner per timeout period */
unsigned int CleanPeriod = MIN_CLEAN_PERIOD;

/* How long a session can be idle before it is cleaned up? */
unsigned int IdleTimeout = MIN_CLEAN_PERIOD * TIMEOUT_DIVISOR;

/* Pipe for breaking select() to initiate periodic cleaning */
int CleanPipe[2];

/* Our relay: if_index followed by peer_mac */
#define MY_RELAY_TAG_LEN (sizeof(int) + ETH_ALEN)

/* Hack for daemonizing */
#define CLOSEFD 64

/**********************************************************************
*%FUNCTION: keepDescriptor
*%ARGUMENTS:
* fd -- a file descriptor
*%RETURNS:
* 1 if descriptor should NOT be closed during daemonizing; 0 otherwise.
***********************************************************************/
static int
keepDescriptor(int fd)
{
    int i;
    if (fd == CleanPipe[0] || fd == CleanPipe[1]) return 1;
    for (i=0; i<NumInterfaces; i++) {
	if (fd == Interfaces[i].discoverySock ||
	    fd == Interfaces[i].sessionSock) return 1;
    }
    return 0;
}

/**********************************************************************
*%FUNCTION: addTag
*%ARGUMENTS:
* packet -- a PPPoE packet
* tag -- tag to add
*%RETURNS:
* -1 if no room in packet; number of bytes added otherwise.
*%DESCRIPTION:
* Inserts a tag as the first tag in a PPPoE packet.
***********************************************************************/
int
addTag(PPPoEPacket *packet, PPPoETag const *tag)
{
    return insertBytes(packet, packet->payload, tag,
		       ntohs(tag->length) + TAG_HDR_SIZE);
}

/**********************************************************************
*%FUNCTION: insertBytes
*%ARGUMENTS:
* packet -- a PPPoE packet
* loc -- location at which to insert bytes of data
* bytes -- the data to insert
* len -- length of data to insert
*%RETURNS:
* -1 if no room in packet; len otherwise.
*%DESCRIPTION:
* Inserts "len" bytes of data at location "loc" in "packet", moving all
* other data up to make room.
***********************************************************************/
int
insertBytes(PPPoEPacket *packet,
	    unsigned char *loc,
	    void const *bytes,
	    int len)
{
    int toMove;
    int plen = ntohs(packet->length);
    /* Sanity checks */
    if (loc < packet->payload ||
	loc > packet->payload + plen ||
	len + plen > MAX_PPPOE_PAYLOAD) {
	return -1;
    }

    toMove = (packet->payload + plen) - loc;
    memmove(loc+len, loc, toMove);
    memcpy(loc, bytes, len);
    packet->length = htons(plen + len);
    return len;
}

/**********************************************************************
*%FUNCTION: removeBytes
*%ARGUMENTS:
* packet -- a PPPoE packet
* loc -- location at which to remove bytes of data
* len -- length of data to remove
*%RETURNS:
* -1 if there was a problem, len otherwise
*%DESCRIPTION:
* Removes "len" bytes of data from location "loc" in "packet", moving all
* other data down to close the gap
***********************************************************************/
int
removeBytes(PPPoEPacket *packet,
	    unsigned char *loc,
	    int len)
{
    int toMove;
    int plen = ntohs(packet->length);
    /* Sanity checks */
    if (len < 0 || len > plen ||
	loc < packet->payload ||
	loc + len > packet->payload + plen) {
	return -1;
    }

    toMove = ((packet->payload + plen) - loc) - len;
    memmove(loc, loc+len, toMove);
    packet->length = htons(plen - len);
    return len;
}

/**********************************************************************
*%FUNCTION: usage
*%ARGUMENTS:
* argv0 -- program name
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Prints usage information and exits.
***********************************************************************/
void
usage(char const *argv0)
{
    fprintf(stderr, "Usage: %s [options]\n", argv0);
    fprintf(stderr, "Options:\n");
    fprintf(stderr, "   -S if_name     -- Specify interface for PPPoE Server\n");
    fprintf(stderr, "   -C if_name     -- Specify interface for PPPoE Client\n");
    fprintf(stderr, "   -B if_name     -- Specify interface for both clients and server\n");
    fprintf(stderr, "   -n nsess       -- Maxmimum number of sessions to relay\n");
    fprintf(stderr, "   -i timeout     -- Idle timeout in seconds (0 = no timeout)\n");
    fprintf(stderr, "   -F             -- Do not fork into background\n");
    fprintf(stderr, "   -h             -- Print this help message\n");

    fprintf(stderr, "\nPPPoE Version %s, Copyright (C) 2001 Roaring Penguin Software Inc.\n", VERSION);
    fprintf(stderr, "PPPoE comes with ABSOLUTELY NO WARRANTY.\n");
    fprintf(stderr, "This is free software, and you are welcome to redistribute it under the terms\n");
    fprintf(stderr, "of the GNU General Public License, version 2 or any later version.\n");
    fprintf(stderr, "http://www.roaringpenguin.com\n");
    exit(EXIT_SUCCESS);
}

/**********************************************************************
*%FUNCTION: main
*%ARGUMENTS:
* argc, argv -- usual suspects
*%RETURNS:
* EXIT_SUCCESS or EXIT_FAILURE
*%DESCRIPTION:
* Main program.  Options:
* -C ifname           -- Use interface for PPPoE clients
* -S ifname           -- Use interface for PPPoE servers
* -B ifname           -- Use interface for both clients and servers
* -n sessions         -- Maximum of "n" sessions
***********************************************************************/
int
main(int argc, char *argv[])
{
    int opt;
    int nsess = DEFAULT_SESSIONS;
    struct sigaction sa;
    int beDaemon = 1;
    openlog("pppoe-relay", LOG_PID, LOG_DAEMON);

    while((opt = getopt(argc, argv, "hC:S:B:n:i:F")) != -1) {
	switch(opt) {
	case 'h':
	    usage(argv[0]);
	    break;
	case 'F':
	    beDaemon = 0;
	    break;
	case 'C':
	    addInterface(optarg, 1, 0);
	    break;
	case 'S':
	    addInterface(optarg, 0, 1);
	    break;
	case 'B':
	    addInterface(optarg, 1, 1);
	    break;
	case 'i':
	    if (sscanf(optarg, "%u", &IdleTimeout) != 1) {
		fprintf(stderr, "Illegal argument to -i: should be -i timeout\n");
		exit(EXIT_FAILURE);
	    }
	    CleanPeriod = IdleTimeout / TIMEOUT_DIVISOR;
	    if (CleanPeriod < MIN_CLEAN_PERIOD) CleanPeriod = MIN_CLEAN_PERIOD;
	    break;
	case 'n':
	    if (sscanf(optarg, "%d", &nsess) != 1) {
		fprintf(stderr, "Illegal argument to -n: should be -n #sessions\n");
		exit(EXIT_FAILURE);
	    }
	    if (nsess < 1 || nsess > 65534) {
		fprintf(stderr, "Illegal argument to -n: must range from 1 to 65534\n");
		exit(EXIT_FAILURE);
	    }
	    break;
	default:
	    usage(argv[0]);
	}
    }

#ifdef USE_LINUX_PACKET
#ifndef HAVE_STRUCT_SOCKADDR_LL
    fprintf(stderr, "The PPPoE relay does not work on Linux 2.0 kernels.\n");
    exit(EXIT_FAILURE);
#endif
#endif

    /* Check that at least two interfaces were defined */
    if (NumInterfaces < 2) {
	fprintf(stderr, "%s: Must define at least two interfaces\n",
		argv[0]);
	exit(EXIT_FAILURE);
    }

    /* Make a pipe for the cleaner */
    if (pipe(CleanPipe) < 0) {
	fatalSys("pipe");
    }

    /* Set up alarm handler */
    sa.sa_handler = alarmHandler;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_RESTART;
    if (sigaction(SIGALRM, &sa, NULL) < 0) {
	fatalSys("sigaction");
    }

    /* Allocate memory for sessions, etc. */
    initRelay(nsess);

    /* Daemonize -- UNIX Network Programming, Vol. 1, Stevens */
    if (beDaemon) {
	int i;
	i = fork();
	if (i < 0) {
	    fatalSys("fork");
	} else if (i != 0) {
	    /* parent */
	    exit(0);
	}
	setsid();
	signal(SIGHUP, SIG_IGN);
	i = fork();
	if (i < 0) {
	    fatalSys("fork");
	} else if (i != 0) {
	    exit(0);
	}

	chdir("/");
	closelog();
	for (i=0; i<CLOSEFD; i++) {
	    if (!keepDescriptor(i)) {
		close(i);
	    }
	}
	/* We nuked our syslog descriptor... */
	openlog("pppoe-relay", LOG_PID, LOG_DAEMON);
    }

    /* Kick off SIGALRM if there is an idle timeout */
    if (IdleTimeout) alarm(1);

    /* Enter the relay loop */
    relayLoop();

    /* Shouldn't ever get here... */
    return EXIT_FAILURE;
}

/**********************************************************************
*%FUNCTION: addInterface
*%ARGUMENTS:
* ifname -- interface name
* clientOK -- true if this interface should relay PADI, PADR packets.
* acOK -- true if this interface should relay PADO, PADS packets.
*%RETURNS:
* Nothing
*%DESCRIPTION:
* Opens an interface; sets up discovery and session sockets.
***********************************************************************/
void
addInterface(char const *ifname,
	     int clientOK,
	     int acOK)
{
    PPPoEInterface *i;
    int j;
    for (j=0; j<NumInterfaces; j++) {
	if (!strncmp(Interfaces[j].name, ifname, IFNAMSIZ)) {
	    fprintf(stderr, "Interface %s specified more than once.\n", ifname);
	    exit(EXIT_FAILURE);
	}
    }

    if (NumInterfaces >= MAX_INTERFACES) {
	fprintf(stderr, "Too many interfaces (%d max)\n",
		MAX_INTERFACES);
	exit(EXIT_FAILURE);
    }
    i = &Interfaces[NumInterfaces++];
    strncpy(i->name, ifname, IFNAMSIZ);
    i->name[IFNAMSIZ] = 0;

    i->discoverySock = openInterface(ifname, Eth_PPPOE_Discovery, i->mac);
    i->sessionSock   = openInterface(ifname, Eth_PPPOE_Session,   NULL);
    i->clientOK = clientOK;
    i->acOK = acOK;