vmxnet3 unable to send IPv6 ESP packets

[Thomas Jansen]

My vmxnet3 network driver (in a closed source custom OS) is unable to send network packets that are structured as follows: Ethernet-Header(IPv6-Header(ESP(encrypted data))). I can verify that the packet is sent in the VM but is dropped in qemu. I first encountered this problem on qemu 2.10.1 but master is affected as well. After some debug printing in qemu I could identify the following call chain as being problematic:

eth_is_ip6_extension_header_type
eth_parse_ipv6_hdr
net_tx_pkt_parse_headers
net_tx_pkt_parse
vmxnet3_process_tx_queue

The problem seems to be the definition of the ESP header (https://en.wikipedia.org/wiki/IPsec#Encapsulating_Security_Payload) that does not follow the standard IPv6 extension header format starting with next type and length. Thus the parsed ext_hdr in eth_parse_ipv6_hdr does not contain valid data, in particular the length will contain bogus data and lead to a info->full_hdr_len that is larger than the packet itself and the loop would then try to read beyond the end of the packet.

Using the e1000 driver I can send these packets. My guess is that the net_tx_pkt_parse function is not called in that case.

My guess for a fix would be to remove "case IP6_ESP:" from eth_is_ip6_extension_header_type and not regard the ESP header as a IPv6 extension header. In a quick test this seems to fix the problem. But that should be verified by someone who is familiar with the code.

[Thomas Huth (th-huth)]

The QEMU project is currently considering to move its bug tracking to another system. For this we need to know which bugs are still valid and which could be closed already. Thus we are setting older bugs to "Incomplete" now.
If you still think this bug report here is valid, then please switch the state back to "New" within the next 60 days, otherwise this report will be marked as "Expired". Or mark it as "Fix Released" if the problem has been solved with a newer version of QEMU already. Thank you and sorry for the inconvenience.

[Thomas Huth (th-huth)]

This is an automated cleanup. This bug report has been moved to QEMU's
new bug tracker on gitlab.com and thus gets marked as 'expired' now.
Please continue with the discussion here:

 https://gitlab.com/qemu-project/qemu/-/issues/149