/*
 * Copyright (c) 1995 Danny Gasparovski.
 *
 * Please read the file COPYRIGHT for the
 * terms and conditions of the copyright.
 */

#include "slirp/slirp.h"

int if_mtu, if_mru;
int if_comp;
int if_maxlinkhdr;
int if_queued = 0;  /* Number of packets queued so far */
int if_thresh = 10; /* Number of packets queued before we start sending
                     * (to prevent allocing too many SLIRPmbufs) */

struct SLIRPmbuf if_fastq;  /* fast queue (for interactive data) */
struct SLIRPmbuf if_batchq; /* queue for non-interactive data */
struct SLIRPmbuf *next_m;   /* Pointer to next SLIRPmbuf to output */

#define ifs_init(ifm) ((ifm)->ifs_next = (ifm)->ifs_prev = (ifm))

void ifs_insque(ifm, ifmhead) struct SLIRPmbuf *ifm, *ifmhead;
{
        ifm->ifs_next = ifmhead->ifs_next;
        ifmhead->ifs_next = ifm;
        ifm->ifs_prev = ifmhead;
        ifm->ifs_next->ifs_prev = ifm;
}

void ifs_remque(ifm) struct SLIRPmbuf *ifm;
{
        ifm->ifs_prev->ifs_next = ifm->ifs_next;
        ifm->ifs_next->ifs_prev = ifm->ifs_prev;
}

void if_init() {
#if 0
	/*
	 * Set if_maxlinkhdr to 48 because it's 40 bytes for TCP/IP,
	 * and 8 bytes for PPP, but need to have it on an 8byte boundary
	 */
#ifdef USE_PPP
	if_maxlinkhdr = 48;
#else
	if_maxlinkhdr = 40;
#endif
#else
        /* 2 for alignment, 14 for ethernet, 40 for TCP/IP */
        if_maxlinkhdr = 2 + 14 + 40;
#endif
        if_mtu = 1500;
        if_mru = 1500;
        if_comp = IF_AUTOCOMP;
        if_fastq.ifq_next = if_fastq.ifq_prev = &if_fastq;
        if_batchq.ifq_next = if_batchq.ifq_prev = &if_batchq;
        //	sl_compress_init(&comp_s);
        next_m = &if_batchq;
}

#if 0
/*
 * This shouldn't be needed since the modem is blocking and
 * we don't expect any signals, but what the hell..
 */
inline int
writen(fd, bptr, n)
	int fd;
	char *bptr;
	int n;
{
	int ret;
	int total;
	
	/* This should succeed most of the time */
	ret = send(fd, bptr, n,0);
	if (ret == n || ret <= 0)
	   return ret;
	
	/* Didn't write everything, go into the loop */
	total = ret;
	while (n > total) {
		ret = send(fd, bptr+total, n-total,0);
		if (ret <= 0)
		   return ret;
		total += ret;
	}
	return total;
}

/*
 * if_input - read() the tty, do "top level" processing (ie: check for any escapes),
 * and pass onto (*ttyp->if_input)
 * 
 * XXXXX Any zeros arriving by themselves are NOT placed into the arriving packet.
 */
#define INBUFF_SIZE 2048 /* XXX */
void
if_input(ttyp)
	struct ttys *ttyp;
{
	u_char if_inbuff[INBUFF_SIZE];
	int if_n;
	
	DEBUG_CALL("if_input");
	DEBUG_ARG("ttyp = %lx", (long)ttyp);
	
	if_n = recv(ttyp->fd, (char *)if_inbuff, INBUFF_SIZE,0);
	
	DEBUG_MISC((dfd, " read %d bytes\n", if_n));
	
	if (if_n <= 0) {
		if (if_n == 0 || (errno != EINTR && errno != EAGAIN)) {
			if (ttyp->up)
			   link_up--;
			tty_detached(ttyp, 0);
		}
		return;
	}
	if (if_n == 1) {
		if (*if_inbuff == '0') {
			ttyp->ones = 0;
			if (++ttyp->zeros >= 5)
			   slirp_exit(0);
			return;
		}
		if (*if_inbuff == '1') {
			ttyp->zeros = 0;
			if (++ttyp->ones >= 5)
			   tty_detached(ttyp, 0);
			return;
		}
	}
	ttyp->ones = ttyp->zeros = 0;
	
	(*ttyp->if_input)(ttyp, if_inbuff, if_n);
}
#endif

/*
 * if_output: Queue packet into an output queue.
 * There are 2 output queue's, if_fastq and if_batchq.
 * Each output queue is a doubly linked list of double linked lists
 * of SLIRPmbufs, each list belonging to one "session" (socket).  This
 * way, we can output packets fairly by sending one packet from each
 * session, instead of all the packets from one session, then all packets
 * from the next session, etc.  Packets on the if_fastq get absolute
 * priority, but if one session hogs the link, it gets "downgraded"
 * to the batchq until it runs out of packets, then it'll return
 * to the fastq (eg. if the user does an ls -alR in a telnet session,
 * it'll temporarily get downgraded to the batchq)
 */
void if_output(so, ifm) struct SLIRPsocket *so;
struct SLIRPmbuf *ifm;
{
        struct SLIRPmbuf *ifq;
        int on_fastq = 1;

        DEBUG_CALL("if_output");
        DEBUG_ARG("so = %lx", (long)so);
        DEBUG_ARG("ifm = %lx", (long)ifm);

        /*
         * First remove the SLIRPmbuf from m_usedlist,
         * since we're gonna use m_next and m_prev ourselves
         * XXX Shouldn't need this, gotta change dtom() etc.
         */
        if (ifm->m_flags & M_USEDLIST) {
                remque(ifm);
                ifm->m_flags &= ~M_USEDLIST;
        }

        /*
         * See if there's already a batchq list for this session.
         * This can include an interactive session, which should go on fastq,
         * but gets too greedy... hence it'll be downgraded from fastq to batchq.
         * We mustn't put this packet back on the fastq (or we'll send it out of order)
         * XXX add cache here?
         */
        for (ifq = if_batchq.ifq_prev; ifq != &if_batchq; ifq = ifq->ifq_prev) {
                if (so == ifq->ifq_so) {
                        /* A match! */
                        ifm->ifq_so = so;
                        ifs_insque(ifm, ifq->ifs_prev);
                        goto diddit;
                }
        }

        /* No match, check which queue to put it on */
        if (so && (so->so_iptos & IPTOS_LOWDELAY)) {
                ifq = if_fastq.ifq_prev;
                on_fastq = 1;
                /*
                 * Check if this packet is a part of the last
                 * packet's session
                 */
                if (ifq->ifq_so == so) {
                        ifm->ifq_so = so;
                        ifs_insque(ifm, ifq->ifs_prev);
                        goto diddit;
                }
        } else
                ifq = if_batchq.ifq_prev;

        /* Create a new doubly linked list for this session */
        ifm->ifq_so = so;
        ifs_init(ifm);
        insque(ifm, ifq);

diddit:
        ++if_queued;

        if (so) {
                /* Update *_queued */
                so->so_queued++;
                so->so_nqueued++;
                /*
                 * Check if the interactive session should be downgraded to
                 * the batchq.  A session is downgraded if it has queued 6
                 * packets without pausing, and at least 3 of those packets
                 * have been sent over the link
                 * (XXX These are arbitrary numbers, probably not optimal..)
                 */
                if (on_fastq && ((so->so_nqueued >= 6) && (so->so_nqueued - so->so_queued) >= 3)) {

                        /* Remove from current queue... */
                        remque(ifm->ifs_next);

                        /* ...And insert in the new.  That'll teach ya! */
                        insque(ifm->ifs_next, &if_batchq);
                }
        }

#ifndef FULL_BOLT
        /*
         * This prevents us from malloc()ing too many SLIRPmbufs
         */
        if (link_up) {
                /* if_start will check towrite */
                if_start();
        }
#endif
}

/*
 * Send a packet
 * We choose a packet based on it's position in the output queues;
 * If there are packets on the fastq, they are sent FIFO, before
 * everything else.  Otherwise we choose the first packet from the
 * batchq and send it.  the next packet chosen will be from the session
 * after this one, then the session after that one, and so on..  So,
 * for example, if there are 3 ftp session's fighting for bandwidth,
 * one packet will be sent from the first session, then one packet
 * from the second session, then one packet from the third, then back
 * to the first, etc. etc.
 */
void if_start(void) {
        struct SLIRPmbuf *ifm, *ifqt;

        DEBUG_CALL("if_start");

        if (if_queued == 0)
                return; /* Nothing to do */

again:
        /* check if we can really output */
        if (!slirp_can_output())
                return;

        /*
         * See which queue to get next packet from
         * If there's something in the fastq, select it immediately
         */
        if (if_fastq.ifq_next != &if_fastq) {
                ifm = if_fastq.ifq_next;
        } else {
                /* Nothing on fastq, see if next_m is valid */
                if (next_m != &if_batchq)
                        ifm = next_m;
                else
                        ifm = if_batchq.ifq_next;

                /* Set which packet to send on next iteration */
                next_m = ifm->ifq_next;
        }
        /* Remove it from the queue */
        ifqt = ifm->ifq_prev;
        remque(ifm);
        --if_queued;

        /* If there are more packets for this session, re-queue them */
        if (ifm->ifs_next != /* ifm->ifs_prev != */ ifm) {
                insque(ifm->ifs_next, ifqt);
                ifs_remque(ifm);
        }

        /* Update so_queued */
        if (ifm->ifq_so) {
                if (--ifm->ifq_so->so_queued == 0)
                        /* If there's no more queued, reset nqueued */
                        ifm->ifq_so->so_nqueued = 0;
        }

        /* Encapsulate the packet for sending */
        if_encap((uint8_t *)ifm->m_data, ifm->m_len);

        m_free(ifm);

        if (if_queued)
                goto again;
}
