File:  [Qemu by Fabrice Bellard] / qemu / slirp / if.c
Revision 1.1.1.5 (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 17:25:42 2018 UTC (3 years, 1 month ago) by root
Branches: qemu, MAIN
CVS tags: qemu1000, qemu0151, qemu0150, qemu0141, qemu0140, qemu0130, qemu0125, qemu0124, qemu0123, qemu0122, qemu0121, qemu0120, qemu0111, qemu0110, HEAD
qemu 0.11.0

    1: /*
    2:  * Copyright (c) 1995 Danny Gasparovski.
    3:  *
    4:  * Please read the file COPYRIGHT for the
    5:  * terms and conditions of the copyright.
    6:  */
    7: 
    8: #include <slirp.h>
    9: 
   10: #define ifs_init(ifm) ((ifm)->ifs_next = (ifm)->ifs_prev = (ifm))
   11: 
   12: static void
   13: ifs_insque(struct mbuf *ifm, struct mbuf *ifmhead)
   14: {
   15: 	ifm->ifs_next = ifmhead->ifs_next;
   16: 	ifmhead->ifs_next = ifm;
   17: 	ifm->ifs_prev = ifmhead;
   18: 	ifm->ifs_next->ifs_prev = ifm;
   19: }
   20: 
   21: static void
   22: ifs_remque(struct mbuf *ifm)
   23: {
   24: 	ifm->ifs_prev->ifs_next = ifm->ifs_next;
   25: 	ifm->ifs_next->ifs_prev = ifm->ifs_prev;
   26: }
   27: 
   28: void
   29: if_init(Slirp *slirp)
   30: {
   31:     slirp->if_fastq.ifq_next = slirp->if_fastq.ifq_prev = &slirp->if_fastq;
   32:     slirp->if_batchq.ifq_next = slirp->if_batchq.ifq_prev = &slirp->if_batchq;
   33:     slirp->next_m = &slirp->if_batchq;
   34: }
   35: 
   36: /*
   37:  * if_output: Queue packet into an output queue.
   38:  * There are 2 output queue's, if_fastq and if_batchq.
   39:  * Each output queue is a doubly linked list of double linked lists
   40:  * of mbufs, each list belonging to one "session" (socket).  This
   41:  * way, we can output packets fairly by sending one packet from each
   42:  * session, instead of all the packets from one session, then all packets
   43:  * from the next session, etc.  Packets on the if_fastq get absolute
   44:  * priority, but if one session hogs the link, it gets "downgraded"
   45:  * to the batchq until it runs out of packets, then it'll return
   46:  * to the fastq (eg. if the user does an ls -alR in a telnet session,
   47:  * it'll temporarily get downgraded to the batchq)
   48:  */
   49: void
   50: if_output(struct socket *so, struct mbuf *ifm)
   51: {
   52: 	Slirp *slirp = ifm->slirp;
   53: 	struct mbuf *ifq;
   54: 	int on_fastq = 1;
   55: 
   56: 	DEBUG_CALL("if_output");
   57: 	DEBUG_ARG("so = %lx", (long)so);
   58: 	DEBUG_ARG("ifm = %lx", (long)ifm);
   59: 
   60: 	/*
   61: 	 * First remove the mbuf from m_usedlist,
   62: 	 * since we're gonna use m_next and m_prev ourselves
   63: 	 * XXX Shouldn't need this, gotta change dtom() etc.
   64: 	 */
   65: 	if (ifm->m_flags & M_USEDLIST) {
   66: 		remque(ifm);
   67: 		ifm->m_flags &= ~M_USEDLIST;
   68: 	}
   69: 
   70: 	/*
   71: 	 * See if there's already a batchq list for this session.
   72: 	 * This can include an interactive session, which should go on fastq,
   73: 	 * but gets too greedy... hence it'll be downgraded from fastq to batchq.
   74: 	 * We mustn't put this packet back on the fastq (or we'll send it out of order)
   75: 	 * XXX add cache here?
   76: 	 */
   77: 	for (ifq = slirp->if_batchq.ifq_prev; ifq != &slirp->if_batchq;
   78: 	     ifq = ifq->ifq_prev) {
   79: 		if (so == ifq->ifq_so) {
   80: 			/* A match! */
   81: 			ifm->ifq_so = so;
   82: 			ifs_insque(ifm, ifq->ifs_prev);
   83: 			goto diddit;
   84: 		}
   85: 	}
   86: 
   87: 	/* No match, check which queue to put it on */
   88: 	if (so && (so->so_iptos & IPTOS_LOWDELAY)) {
   89: 		ifq = slirp->if_fastq.ifq_prev;
   90: 		on_fastq = 1;
   91: 		/*
   92: 		 * Check if this packet is a part of the last
   93: 		 * packet's session
   94: 		 */
   95: 		if (ifq->ifq_so == so) {
   96: 			ifm->ifq_so = so;
   97: 			ifs_insque(ifm, ifq->ifs_prev);
   98: 			goto diddit;
   99: 		}
  100: 	} else
  101: 		ifq = slirp->if_batchq.ifq_prev;
  102: 
  103: 	/* Create a new doubly linked list for this session */
  104: 	ifm->ifq_so = so;
  105: 	ifs_init(ifm);
  106: 	insque(ifm, ifq);
  107: 
  108: diddit:
  109: 	slirp->if_queued++;
  110: 
  111: 	if (so) {
  112: 		/* Update *_queued */
  113: 		so->so_queued++;
  114: 		so->so_nqueued++;
  115: 		/*
  116: 		 * Check if the interactive session should be downgraded to
  117: 		 * the batchq.  A session is downgraded if it has queued 6
  118: 		 * packets without pausing, and at least 3 of those packets
  119: 		 * have been sent over the link
  120: 		 * (XXX These are arbitrary numbers, probably not optimal..)
  121: 		 */
  122: 		if (on_fastq && ((so->so_nqueued >= 6) &&
  123: 				 (so->so_nqueued - so->so_queued) >= 3)) {
  124: 
  125: 			/* Remove from current queue... */
  126: 			remque(ifm->ifs_next);
  127: 
  128: 			/* ...And insert in the new.  That'll teach ya! */
  129: 			insque(ifm->ifs_next, &slirp->if_batchq);
  130: 		}
  131: 	}
  132: 
  133: #ifndef FULL_BOLT
  134: 	/*
  135: 	 * This prevents us from malloc()ing too many mbufs
  136: 	 */
  137: 	if_start(ifm->slirp);
  138: #endif
  139: }
  140: 
  141: /*
  142:  * Send a packet
  143:  * We choose a packet based on it's position in the output queues;
  144:  * If there are packets on the fastq, they are sent FIFO, before
  145:  * everything else.  Otherwise we choose the first packet from the
  146:  * batchq and send it.  the next packet chosen will be from the session
  147:  * after this one, then the session after that one, and so on..  So,
  148:  * for example, if there are 3 ftp session's fighting for bandwidth,
  149:  * one packet will be sent from the first session, then one packet
  150:  * from the second session, then one packet from the third, then back
  151:  * to the first, etc. etc.
  152:  */
  153: void
  154: if_start(Slirp *slirp)
  155: {
  156: 	struct mbuf *ifm, *ifqt;
  157: 
  158: 	DEBUG_CALL("if_start");
  159: 
  160: 	if (slirp->if_queued == 0)
  161: 	   return; /* Nothing to do */
  162: 
  163:  again:
  164:         /* check if we can really output */
  165:         if (!slirp_can_output(slirp->opaque))
  166:             return;
  167: 
  168: 	/*
  169: 	 * See which queue to get next packet from
  170: 	 * If there's something in the fastq, select it immediately
  171: 	 */
  172: 	if (slirp->if_fastq.ifq_next != &slirp->if_fastq) {
  173: 		ifm = slirp->if_fastq.ifq_next;
  174: 	} else {
  175: 		/* Nothing on fastq, see if next_m is valid */
  176: 		if (slirp->next_m != &slirp->if_batchq)
  177: 		   ifm = slirp->next_m;
  178: 		else
  179: 		   ifm = slirp->if_batchq.ifq_next;
  180: 
  181: 		/* Set which packet to send on next iteration */
  182: 		slirp->next_m = ifm->ifq_next;
  183: 	}
  184: 	/* Remove it from the queue */
  185: 	ifqt = ifm->ifq_prev;
  186: 	remque(ifm);
  187: 	slirp->if_queued--;
  188: 
  189: 	/* If there are more packets for this session, re-queue them */
  190: 	if (ifm->ifs_next != /* ifm->ifs_prev != */ ifm) {
  191: 		insque(ifm->ifs_next, ifqt);
  192: 		ifs_remque(ifm);
  193: 	}
  194: 
  195: 	/* Update so_queued */
  196: 	if (ifm->ifq_so) {
  197: 		if (--ifm->ifq_so->so_queued == 0)
  198: 		   /* If there's no more queued, reset nqueued */
  199: 		   ifm->ifq_so->so_nqueued = 0;
  200: 	}
  201: 
  202: 	/* Encapsulate the packet for sending */
  203:         if_encap(slirp, (uint8_t *)ifm->m_data, ifm->m_len);
  204: 
  205:         m_free(ifm);
  206: 
  207: 	if (slirp->if_queued)
  208: 	   goto again;
  209: }

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