Hello,
commit 9c46f6d42f1b5627c49a5906cb5b315ad8716ff0
Author: Alex Williamson <[email protected]>
Date: Wed Feb 4 16:36:34 2009 -0800
virtio_net: Allow setting the MAC address of the NIC
Introduced an unconditional config->set to the MAC address field of
the device config.
+ } else {
random_ether_addr(dev->dev_addr);
+ vdev->config->set(vdev, offsetof(struct virtio_net_config, mac),
+ dev->dev_addr, dev->addr_len);
+ }
Since our kuli userspace sample does not set VIRTIO_NET_F_MAC, there is no
config space assigned for this device. When virtio_net tries to overwrite
the non-existing field, this triggers a bug.
virtio_net.h specifies:
struct virtio_net_config
{
/* The config defining mac address (if VIRTIO_NET_F_MAC) */
__u8 mac[6];
[...]
I read this as the mac config field is optional (similar to all the optional
fields we added in virtio_blk later).
I see two options:
1. Change our sample userspace to always allocate the config (like lguest and
qemu)
2. Change the kernel code to not write into the config unless a specific feature
bit is set. (e.g. VIRTIO_NET_F_SETMAC)
Opinions?
PS: The same is true for virtnet_set_mac_address. it crashes as well
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