firewire: net: max MTU off by one

The latest max_mtu patch missed that datagram_size is actually one less
than the datagram's Total Length.

Fixes: 357f4aae859b ("firewire: net: really fix maximum possible MTU")
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/firewire/net.c b/drivers/firewire/net.c
index 242359c2d1f1..60e75e6d9104 100644
--- a/drivers/firewire/net.c
+++ b/drivers/firewire/net.c
@@ -1480,9 +1480,14 @@ static int fwnet_probe(struct fw_unit *unit,
                 goto out;
         dev->local_fifo = dev->handler.offset;
 
+        /*
+         * default MTU: RFC 2734 cl. 4, RFC 3146 cl. 4
+         * maximum MTU: RFC 2734 cl. 4.2, fragment encapsulation header's
+         *              maximum possible datagram_size + 1 = 0xfff + 1
+         */
         net->mtu = 1500U;
         net->min_mtu = ETH_MIN_MTU;
-        net->max_mtu = 0xfff;
+        net->max_mtu = 4096U;
 
         /* Set our hardware address while we're at it */
         ha = (union fwnet_hwaddr *)net->dev_addr;