From e9300a4b7bbae83af1f7703938c94cf6dc6d308f Mon Sep 17 00:00:00 2001 From: Stefan Richter Date: Sun, 30 Oct 2016 17:32:01 +0100 Subject: [PATCH] firewire: net: fix fragmented datagram_size off-by-one RFC 2734 defines the datagram_size field in fragment encapsulation headers thus: datagram_size: The encoded size of the entire IP datagram. The value of datagram_size [...] SHALL be one less than the value of Total Length in the datagram's IP header (see STD 5, RFC 791). Accordingly, the eth1394 driver of Linux 2.6.36 and older set and got this field with a -/+1 offset: ether1394_tx() /* transmit */ ether1394_encapsulate_prep() hdr->ff.dg_size = dg_size - 1; ether1394_data_handler() /* receive */ if (hdr->common.lf == ETH1394_HDR_LF_FF) dg_size = hdr->ff.dg_size + 1; else dg_size = hdr->sf.dg_size + 1; Likewise, I observe OS X 10.4 and Windows XP Pro SP3 to transmit 1500 byte sized datagrams in fragments with datagram_size=1499 if link fragmentation is required. Only firewire-net sets and gets datagram_size without this offset. The result is lacking interoperability of firewire-net with OS X, Windows XP, and presumably Linux' eth1394. (I did not test with the latter.) For example, FTP data transfers to a Linux firewire-net box with max_rec smaller than the 1500 bytes MTU - from OS X fail entirely, - from Win XP start out with a bunch of fragmented datagrams which time out, then continue with unfragmented datagrams because Win XP temporarily reduces the MTU to 576 bytes. So let's fix firewire-net's datagram_size accessors. Note that firewire-net thereby loses interoperability with unpatched firewire-net, but only if link fragmentation is employed. (This happens with large broadcast datagrams, and with large datagrams on several FireWire CardBus cards with smaller max_rec than equivalent PCI cards, and it can be worked around by setting a small enough MTU.) Cc: stable@vger.kernel.org Signed-off-by: Stefan Richter --- drivers/firewire/net.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/firewire/net.c b/drivers/firewire/net.c index cbaa8d776d83..15475892af0c 100644 --- a/drivers/firewire/net.c +++ b/drivers/firewire/net.c @@ -73,13 +73,13 @@ struct rfc2734_header { #define fwnet_get_hdr_lf(h) (((h)->w0 & 0xc0000000) >> 30) #define fwnet_get_hdr_ether_type(h) (((h)->w0 & 0x0000ffff)) -#define fwnet_get_hdr_dg_size(h) (((h)->w0 & 0x0fff0000) >> 16) +#define fwnet_get_hdr_dg_size(h) ((((h)->w0 & 0x0fff0000) >> 16) + 1) #define fwnet_get_hdr_fg_off(h) (((h)->w0 & 0x00000fff)) #define fwnet_get_hdr_dgl(h) (((h)->w1 & 0xffff0000) >> 16) -#define fwnet_set_hdr_lf(lf) ((lf) << 30) +#define fwnet_set_hdr_lf(lf) ((lf) << 30) #define fwnet_set_hdr_ether_type(et) (et) -#define fwnet_set_hdr_dg_size(dgs) ((dgs) << 16) +#define fwnet_set_hdr_dg_size(dgs) (((dgs) - 1) << 16) #define fwnet_set_hdr_fg_off(fgo) (fgo) #define fwnet_set_hdr_dgl(dgl) ((dgl) << 16) @@ -622,7 +622,7 @@ static int fwnet_incoming_packet(struct fwnet_device *dev, __be32 *buf, int len, fg_off = fwnet_get_hdr_fg_off(&hdr); } datagram_label = fwnet_get_hdr_dgl(&hdr); - dg_size = fwnet_get_hdr_dg_size(&hdr); /* ??? + 1 */ + dg_size = fwnet_get_hdr_dg_size(&hdr); if (fg_off + len > dg_size) return 0; -- 2.39.5