Archipelago » qemu

/*

 * Copyright (c) 1995 Danny Gasparovski.

 *

 * Please read the file COPYRIGHT for the

 * terms and conditions of the copyright.

 */

#include <slirp.h>

#include "qemu/timer.h"

static void

ifs_insque(struct mbuf *ifm, struct mbuf *ifmhead)

{

        ifm->ifs_next = ifmhead->ifs_next;

        ifmhead->ifs_next = ifm;

        ifm->ifs_prev = ifmhead;

        ifm->ifs_next->ifs_prev = ifm;

}

static void

ifs_remque(struct mbuf *ifm)

{

        ifm->ifs_prev->ifs_next = ifm->ifs_next;

        ifm->ifs_next->ifs_prev = ifm->ifs_prev;

}

void

if_init(Slirp *slirp)

{

    slirp->if_fastq.ifq_next = slirp->if_fastq.ifq_prev = &slirp->if_fastq;

    slirp->if_batchq.ifq_next = slirp->if_batchq.ifq_prev = &slirp->if_batchq;

    slirp->next_m = &slirp->if_batchq;

}

/*

 * 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 mbufs, 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(struct socket *so, struct mbuf *ifm)

{

        Slirp *slirp = ifm->slirp;

        struct mbuf *ifq;

        int on_fastq = 1;

        DEBUG_CALL("if_output");

        DEBUG_ARG("so = %lx", (long)so);

        DEBUG_ARG("ifm = %lx", (long)ifm);

        /*

         * First remove the mbuf 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 = slirp->if_batchq.ifq_prev; ifq != &slirp->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 = slirp->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 = slirp->if_batchq.ifq_prev;

                /* Set next_m if the queue was empty so far */

                if (slirp->next_m == &slirp->if_batchq) {

                    slirp->next_m = ifm;

                }

        }

        /* Create a new doubly linked list for this session */

        ifm->ifq_so = so;

        ifs_init(ifm);

        insque(ifm, ifq);

diddit:

        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, &slirp->if_batchq);

                }

        }

#ifndef FULL_BOLT

        /*

         * This prevents us from malloc()ing too many mbufs

         */

        if_start(ifm->slirp);

#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(Slirp *slirp)

{

    uint64_t now = qemu_get_clock_ns(rt_clock);

    bool from_batchq, next_from_batchq;

    struct mbuf *ifm, *ifm_next, *ifqt;

    DEBUG_CALL("if_start");

    if (slirp->if_start_busy) {

        return;

    }

    slirp->if_start_busy = true;

    if (slirp->if_fastq.ifq_next != &slirp->if_fastq) {

        ifm_next = slirp->if_fastq.ifq_next;

        next_from_batchq = false;

    } else if (slirp->next_m != &slirp->if_batchq) {

        /* Nothing on fastq, pick up from batchq via next_m */

        ifm_next = slirp->next_m;

        next_from_batchq = true;

    } else {

        ifm_next = NULL;

    }

    while (ifm_next) {

        ifm = ifm_next;

        from_batchq = next_from_batchq;

        ifm_next = ifm->ifq_next;

        if (ifm_next == &slirp->if_fastq) {

            /* No more packets in fastq, switch to batchq */

            ifm_next = slirp->next_m;

            next_from_batchq = true;

        }

        if (ifm_next == &slirp->if_batchq) {

            /* end of batchq */

            ifm_next = NULL;

        }

        /* Try to send packet unless it already expired */

        if (ifm->expiration_date >= now && !if_encap(slirp, ifm)) {

            /* Packet is delayed due to pending ARP resolution */

            continue;

        }

        if (ifm == slirp->next_m) {

            /* Set which packet to send on next iteration */

            slirp->next_m = ifm->ifq_next;

        }

        /* Remove it from the queue */

        ifqt = ifm->ifq_prev;

        remque(ifm);

        /* If there are more packets for this session, re-queue them */

        if (ifm->ifs_next != ifm) {

            struct mbuf *next = ifm->ifs_next;

            insque(next, ifqt);

            ifs_remque(ifm);

            if (!from_batchq) {

                /* Next packet in fastq is from the same session */

                ifm_next = next;

                next_from_batchq = false;

            } else if (slirp->next_m == &slirp->if_batchq) {

                /* Set next_m and ifm_next if the session packet is now the

                 * only one on batchq */

                slirp->next_m = ifm_next = next;

            }

        }

        /* Update so_queued */

        if (ifm->ifq_so && --ifm->ifq_so->so_queued == 0) {

            /* If there's no more queued, reset nqueued */

            ifm->ifq_so->so_nqueued = 0;

        }

        m_free(ifm);

    }

    slirp->if_start_busy = false;

}