From 70fc25ad6e71a99b5802eb92b95c26407acbe990 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Wed, 25 Jan 2017 14:48:24 +0000 Subject: [netdevice] Limit MTU by hardware maximum frame length Separate out the concept of "hardware maximum supported frame length" and "configured link MTU", and limit the latter according to the former. In networks where the DHCP-supplied link MTU is inconsistent with the hardware or driver capabilities (e.g. a network using jumbo frames), this will result in iPXE advertising a TCP MSS consistent with a size that can actually be received. Note that the term "MTU" is typically used to refer to the maximum length excluding the link-layer headers; we adopt this usage. Signed-off-by: Michael Brown --- src/net/netdevice.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'src/net/netdevice.c') diff --git a/src/net/netdevice.c b/src/net/netdevice.c index 9df21196c..41ece77f0 100644 --- a/src/net/netdevice.c +++ b/src/net/netdevice.c @@ -663,6 +663,12 @@ int register_netdev ( struct net_device *netdev ) { ll_protocol->init_addr ( netdev->hw_addr, netdev->ll_addr ); } + /* Set MTU, if not already set */ + if ( ! netdev->mtu ) { + netdev->mtu = ( netdev->max_pkt_len - + ll_protocol->ll_header_len ); + } + /* Reject network devices that are already available via a * different hardware device. */ -- cgit v1.2.3-55-g7522