802.11 fragment handling functions

Functions
static void	net80211_free_frags (struct net80211_device *dev, int fcid)
	Free buffers used by 802.11 fragment cache entry. More...
static struct io_buffer *	net80211_accum_frags (struct net80211_device *dev, int fcid, int nfrags, int size)
	Accumulate 802.11 fragments into one I/O buffer. More...
static void	net80211_rx_frag (struct net80211_device *dev, struct io_buffer *iob, int signal)
	Handle receipt of 802.11 fragment. More...

Detailed Description

Function Documentation

net80211_free_frags()

static void net80211_free_frags ( struct net80211_device *  dev, int  fcid  )

static

Free buffers used by 802.11 fragment cache entry.

Parameters

dev	802.11 device
fcid	Fragment cache entry index

After this function, the referenced entry will be marked unused.

Definition at line 2534 of file net80211.c.

{
        int j;
        struct net80211_frag_cache *frag = &dev->frags[fcid];

        for ( j = 0; j < 16; j++ ) {
                if ( frag->iob[j] ) {
                        free_iob ( frag->iob[j] );
                        frag->iob[j] = NULL;
                }
        }

        frag->seqnr = 0;
        frag->start_ticks = 0;
        frag->in_use = 0;
}

References net80211_device::frags, free_iob(), net80211_frag_cache::in_use, net80211_frag_cache::iob, NULL, net80211_frag_cache::seqnr, and net80211_frag_cache::start_ticks.

Referenced by net80211_rx_frag().

net80211_accum_frags()

static struct io_buffer * net80211_accum_frags ( struct net80211_device *  dev, int  fcid, int  nfrags, int  size  )

static

Accumulate 802.11 fragments into one I/O buffer.

Parameters

dev	802.11 device
fcid	Fragment cache entry index
nfrags	Number of fragments received
size	Sum of sizes of all fragments, including headers

Return values

iob	I/O buffer containing reassembled packet

This function does not free the fragment buffers.

Definition at line 2562 of file net80211.c.

{
        struct net80211_frag_cache *frag = &dev->frags[fcid];
        int hdrsize = IEEE80211_TYP_FRAME_HEADER_LEN;
        int nsize = size - hdrsize * ( nfrags - 1 );
        int i;

        struct io_buffer *niob = alloc_iob ( nsize );
        struct ieee80211_frame *hdr;

        /* Add the header from the first one... */
        memcpy ( iob_put ( niob, hdrsize ), frag->iob[0]->data, hdrsize );

        /* ... and all the data from all of them. */
        for ( i = 0; i < nfrags; i++ ) {
                int len = iob_len ( frag->iob[i] ) - hdrsize;
                memcpy ( iob_put ( niob, len ),
                         frag->iob[i]->data + hdrsize, len );
        }

        /* Turn off the fragment bit. */
        hdr = niob->data;
        hdr->fc &= ~IEEE80211_FC_MORE_FRAG;

        return niob;
}

References alloc_iob(), io_buffer::data, net80211_device::frags, hdr, IEEE80211_FC_MORE_FRAG, IEEE80211_TYP_FRAME_HEADER_LEN, net80211_frag_cache::iob, iob_len(), iob_put, len, memcpy(), and size.

Referenced by net80211_rx_frag().

net80211_rx_frag()

static void net80211_rx_frag ( struct net80211_device *  dev, struct io_buffer *  iob, int  signal  )

static

Handle receipt of 802.11 fragment.

Parameters

dev	802.11 device
iob	I/O buffer containing fragment
signal	Signal strength with which fragment was received

Definition at line 2597 of file net80211.c.

{
        struct ieee80211_frame *hdr = iob->data;
        int fragnr = IEEE80211_FRAG ( hdr->seq );

        if ( fragnr == 0 && ( hdr->fc & IEEE80211_FC_MORE_FRAG ) ) {
                /* start a frag cache entry */
                int i, newest = -1;
                u32 curr_ticks = currticks(), newest_ticks = 0;
                u32 timeout = TICKS_PER_SEC * NET80211_FRAG_TIMEOUT;

                for ( i = 0; i < NET80211_NR_CONCURRENT_FRAGS; i++ ) {
                        if ( dev->frags[i].in_use == 0 )
                                break;

                        if ( dev->frags[i].start_ticks + timeout >=
                             curr_ticks ) {
                                net80211_free_frags ( dev, i );
                                break;
                        }

                        if ( dev->frags[i].start_ticks > newest_ticks ) {
                                newest = i;
                                newest_ticks = dev->frags[i].start_ticks;
                        }
                }

                /* If we're being sent more concurrent fragmented
                   packets than we can handle, drop the newest so the
                   older ones have time to complete. */
                if ( i == NET80211_NR_CONCURRENT_FRAGS ) {
                        i = newest;
                        net80211_free_frags ( dev, i );
                }

                dev->frags[i].in_use = 1;
                dev->frags[i].seqnr = IEEE80211_SEQNR ( hdr->seq );
                dev->frags[i].start_ticks = currticks();
                dev->frags[i].iob[0] = iob;
                return;
        } else {
                int i;
                for ( i = 0; i < NET80211_NR_CONCURRENT_FRAGS; i++ ) {
                        if ( dev->frags[i].in_use && dev->frags[i].seqnr ==
                             IEEE80211_SEQNR ( hdr->seq ) )
                                break;
                }
                if ( i == NET80211_NR_CONCURRENT_FRAGS ) {
                        /* Drop non-first not-in-cache fragments */
                        DBGC ( dev, "802.11 %p dropped fragment fc=%04x "
                               "seq=%04x\n", dev, hdr->fc, hdr->seq );
                        free_iob ( iob );
                        return;
                }

                dev->frags[i].iob[fragnr] = iob;

                if ( ! ( hdr->fc & IEEE80211_FC_MORE_FRAG ) ) {
                        int j, size = 0;
                        for ( j = 0; j < fragnr; j++ ) {
                                size += iob_len ( dev->frags[i].iob[j] );
                                if ( dev->frags[i].iob[j] == NULL )
                                        break;
                        }
                        if ( j == fragnr ) {
                                /* We've got everything */
                                struct io_buffer *niob =
                                    net80211_accum_frags ( dev, i, fragnr,
                                                           size );
                                net80211_free_frags ( dev, i );
                                net80211_rx ( dev, niob, signal, 0 );
                        } else {
                                DBGC ( dev, "802.11 %p dropping fragmented "
                                       "packet due to out-of-order arrival, "
                                       "fc=%04x seq=%04x\n", dev, hdr->fc,
                                       hdr->seq );
                                net80211_free_frags ( dev, i );
                        }
                }
        }
}

References currticks(), io_buffer::data, DBGC, net80211_device::frags, free_iob(), hdr, IEEE80211_FC_MORE_FRAG, IEEE80211_FRAG, IEEE80211_SEQNR, net80211_frag_cache::in_use, net80211_frag_cache::iob, iob_len(), net80211_accum_frags(), NET80211_FRAG_TIMEOUT, net80211_free_frags(), NET80211_NR_CONCURRENT_FRAGS, net80211_rx(), NULL, net80211_frag_cache::seqnr, size, net80211_frag_cache::start_ticks, TICKS_PER_SEC, and timeout().

Referenced by net80211_rx().