1 files changed, 110 insertions, 67 deletions

diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c
index 3b377f6cd4a0..ad4b58af6b76 100644
--- a/drivers/net/ppp_generic.c
+++ b/drivers/net/ppp_generic.c
@@ -1217,36 +1217,43 @@ ppp_push(struct ppp *ppp)
  */
 static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb)
 {
-        int nch, len, fragsize;
+        int len, fragsize;
         int i, bits, hdrlen, mtu;
-        int flen, fnb;
+        int flen;
+        int navail, nfree;
+        int nbigger;
         unsigned char *p, *q;
         struct list_head *list;
         struct channel *pch;
         struct sk_buff *frag;
         struct ppp_channel *chan;
 
-        nch = 0;
+        nfree = 0;      /* # channels which have no packet already queued */
+        navail = 0;     /* total # of usable channels (not deregistered) */
         hdrlen = (ppp->flags & SC_MP_XSHORTSEQ)? MPHDRLEN_SSN: MPHDRLEN;
+        i = 0;
         list = &ppp->channels;
         while ((list = list->next) != &ppp->channels) {
                 pch = list_entry(list, struct channel, clist);
-                nch += pch->avail = (skb_queue_len(&pch->file.xq) == 0);
-                /*
-                 * If a channel hasn't had a fragment yet, it has to get
-                 * one before we send any fragments on later channels.
-                 * If it can't take a fragment now, don't give any
-                 * to subsequent channels.
-                 */
-                if (!pch->had_frag && !pch->avail) {
-                        while ((list = list->next) != &ppp->channels) {
-                                pch = list_entry(list, struct channel, clist);
-                                pch->avail = 0;
+                navail += pch->avail = (pch->chan != NULL);
+                if (pch->avail) {
+                        if (skb_queue_len(&pch->file.xq) == 0
+                            || !pch->had_frag) {
+                                pch->avail = 2;
+                                ++nfree;
                         }
-                        break;
+                        if (!pch->had_frag && i < ppp->nxchan)
+                                ppp->nxchan = i;
                 }
+                ++i;
         }
-        if (nch == 0)
+
+        /*
+         * Don't start sending this packet unless at least half of
+         * the channels are free.  This gives much better TCP
+         * performance if we have a lot of channels.
+         */
+        if (nfree == 0 || nfree < navail / 2)
                 return 0;       /* can't take now, leave it in xmit_pending */
 
         /* Do protocol field compression (XXX this should be optional) */
@@ -1257,14 +1264,19 @@ static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb)
                 --len;
         }
 
-        /* decide on fragment size */
+        /*
+         * Decide on fragment size.
+         * We create a fragment for each free channel regardless of
+         * how small they are (i.e. even 0 length) in order to minimize
+         * the time that it will take to detect when a channel drops
+         * a fragment.
+         */
         fragsize = len;
-        if (nch > 1) {
-                int maxch = ROUNDUP(len, MIN_FRAG_SIZE);
-                if (nch > maxch)
-                        nch = maxch;
-                fragsize = ROUNDUP(fragsize, nch);
-        }
+        if (nfree > 1)
+                fragsize = ROUNDUP(fragsize, nfree);
+        /* nbigger channels get fragsize bytes, the rest get fragsize-1,
+           except if nbigger==0, then they all get fragsize. */
+        nbigger = len % nfree;
 
         /* skip to the channel after the one we last used
            and start at that one */
@@ -1278,7 +1290,7 @@ static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb)
 
         /* create a fragment for each channel */
         bits = B;
-        do {
+        while (nfree > 0 || len > 0) {
                 list = list->next;
                 if (list == &ppp->channels) {
                         i = 0;
@@ -1289,61 +1301,92 @@ static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb)
                 if (!pch->avail)
                         continue;
 
+                /*
+                 * Skip this channel if it has a fragment pending already and
+                 * we haven't given a fragment to all of the free channels.
+                 */
+                if (pch->avail == 1) {
+                        if (nfree > 0)
+                                continue;
+                } else {
+                        --nfree;
+                        pch->avail = 1;
+                }
+
                 /* check the channel's mtu and whether it is still attached. */
                 spin_lock_bh(&pch->downl);
-                if (pch->chan == 0 || (mtu = pch->chan->mtu) < hdrlen) {
-                        /* can't use this channel */
+                if (pch->chan == NULL) {
+                        /* can't use this channel, it's being deregistered */
                         spin_unlock_bh(&pch->downl);
                         pch->avail = 0;
-                        if (--nch == 0)
+                        if (--navail == 0)
                                 break;
                         continue;
                 }
 
                 /*
-                 * We have to create multiple fragments for this channel
-                 * if fragsize is greater than the channel's mtu.
+                 * Create a fragment for this channel of
+                 * min(max(mtu+2-hdrlen, 4), fragsize, len) bytes.
+                 * If mtu+2-hdrlen < 4, that is a ridiculously small
+                 * MTU, so we use mtu = 2 + hdrlen.
                  */
                 if (fragsize > len)
                         fragsize = len;
-                for (flen = fragsize; flen > 0; flen -= fnb) {
-                        fnb = flen;
-                        if (fnb > mtu + 2 - hdrlen)
-                                fnb = mtu + 2 - hdrlen;
-                        if (fnb >= len)
-                                bits |= E;
-                        frag = alloc_skb(fnb + hdrlen, GFP_ATOMIC);
-                        if (frag == 0)
-                                goto noskb;
-                        q = skb_put(frag, fnb + hdrlen);
-                        /* make the MP header */
-                        q[0] = PPP_MP >> 8;
-                        q[1] = PPP_MP;
-                        if (ppp->flags & SC_MP_XSHORTSEQ) {
-                                q[2] = bits + ((ppp->nxseq >> 8) & 0xf);
-                                q[3] = ppp->nxseq;
-                        } else {
-                                q[2] = bits;
-                                q[3] = ppp->nxseq >> 16;
-                                q[4] = ppp->nxseq >> 8;
-                                q[5] = ppp->nxseq;
-                        }
-
-                        /* copy the data in */
-                        memcpy(q + hdrlen, p, fnb);
-
-                        /* try to send it down the channel */
-                        chan = pch->chan;
-                        if (!chan->ops->start_xmit(chan, frag))
-                                skb_queue_tail(&pch->file.xq, frag);
-                        pch->had_frag = 1;
-                        p += fnb;
-                        len -= fnb;
-                        ++ppp->nxseq;
-                        bits = 0;
+                flen = fragsize;
+                mtu = pch->chan->mtu + 2 - hdrlen;
+                if (mtu < 4)
+                        mtu = 4;
+                if (flen > mtu)
+                        flen = mtu;
+                if (flen == len && nfree == 0)
+                        bits |= E;
+                frag = alloc_skb(flen + hdrlen + (flen == 0), GFP_ATOMIC);
+                if (frag == 0)
+                        goto noskb;
+                q = skb_put(frag, flen + hdrlen);
+
+                /* make the MP header */
+                q[0] = PPP_MP >> 8;
+                q[1] = PPP_MP;
+                if (ppp->flags & SC_MP_XSHORTSEQ) {
+                        q[2] = bits + ((ppp->nxseq >> 8) & 0xf);
+                        q[3] = ppp->nxseq;
+                } else {
+                        q[2] = bits;
+                        q[3] = ppp->nxseq >> 16;
+                        q[4] = ppp->nxseq >> 8;
+                        q[5] = ppp->nxseq;
                 }
+
+                /*
+                 * Copy the data in.
+                 * Unfortunately there is a bug in older versions of
+                 * the Linux PPP multilink reconstruction code where it
+                 * drops 0-length fragments.  Therefore we make sure the
+                 * fragment has at least one byte of data.  Any bytes
+                 * we add in this situation will end up as padding on the
+                 * end of the reconstructed packet.
+                 */
+                if (flen == 0)
+                        *skb_put(frag, 1) = 0;
+                else
+                        memcpy(q + hdrlen, p, flen);
+
+                /* try to send it down the channel */
+                chan = pch->chan;
+                if (skb_queue_len(&pch->file.xq)
+                    || !chan->ops->start_xmit(chan, frag))
+                        skb_queue_tail(&pch->file.xq, frag);
+                pch->had_frag = 1;
+                p += flen;
+                len -= flen;
+                ++ppp->nxseq;
+                bits = 0;
                 spin_unlock_bh(&pch->downl);
-        } while (len > 0);
+
+                if (--nbigger == 0 && fragsize > 0)
+                        --fragsize;
+        }
         ppp->nxchan = i;
 
         return 1;
@@ -1422,7 +1465,7 @@ ppp_input(struct ppp_channel *chan, struct sk_buff *skb)
                 kfree_skb(skb);
                 return;
         }
-        
+
         proto = PPP_PROTO(skb);
         read_lock_bh(&pch->upl);
         if (pch->ppp == 0 || proto >= 0xc000 || proto == PPP_CCPFRAG) {
@@ -1691,7 +1734,7 @@ ppp_receive_mp_frame(struct ppp *ppp, struct sk_buff *skb, struct channel *pch)
         struct list_head *l;
         int mphdrlen = (ppp->flags & SC_MP_SHORTSEQ)? MPHDRLEN_SSN: MPHDRLEN;
 
-        if (!pskb_may_pull(skb, mphdrlen + 1) || ppp->mrru == 0)
+        if (!pskb_may_pull(skb, mphdrlen) || ppp->mrru == 0)
                 goto err;               /* no good, throw it away */
 
         /* Decode sequence number and begin/end bits */