Some protocols (such as ARP) may modify the received packet and re-use
the same I/O buffer for transmission of a reply. The SMSC95XX
transmit header is larger than the receive header: the re-used I/O
buffer therefore does not have sufficient headroom for the transmit
header, and the ARP reply will therefore fail to be transmitted. This
is essentially the same problem as in commit 2e72d10 ("[ncm] Reserve
headroom in received packets").
Fix by reserving sufficient space at the start of each received packet
to allow for the difference between the lengths of the transmit and
receive headers.
This problem is not caught by the current driver development test
suite (documented at http://ipxe.org/dev/driver), since even the large
file transfer tests tend to completely sufficiently quickly that there
is no need for the server to ever send an ARP request. The failure
shows up only when using a very slow protocol such as RFC7440-enhanced
TFTP (as used by Windows Deployment Services).
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The LED pins are configured by default as GPIO inputs. While it is
conceivable that a board might actually use these pins as GPIOs, no
such board is known to exist.
The Linux smsc95xx driver configures these pins unconditionally as LED
outputs. Assume that it is safe to do likewise.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The SMSC95xx devices tend to be used in embedded systems with a
variety of ad-hoc mechanisms for storing the MAC address.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Tested using QEMU and usbredir to expose the LAN9512 chip present on a
Raspberry Pi.
There is a known issue with the LAN9512: an extra two bytes are
appended to every transmitted packet. These two bytes comprise:
{ 0x00, 0x08 } if packet length == 0 (mod 8)
{ CRC[0], 0x00 } if packet length == 7 (mod 8)
{ CRC[0], CRC[1] } otherwise
The extra bytes are appended whether the Ethernet CRC is generated
manually or added automatically by the hardware. The issue occurs
with the Linux kernel driver as well as the iPXE driver. It appears
to be an undocumented hardware errata.
TCP/IP traffic is not affected, since the IP header length field
causes the extraneous bytes to be discarded by the receiver. However,
protocols that rely on the length of the Ethernet frame (such as FCoE
or iPXE's "lotest" protocol) will be unusable on this hardware.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown