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Packet sockets, like tap, can be used as the backend for kernel vhost. In packet sockets, virtio net header size is currently hardcoded to be the size of struct virtio_net_hdr, which is 10 bytes; however, it is not always the case: some virtio features, such as mrg_rxbuf, need virtio net header to be 12-byte long. Mergeable buffers, as a virtio feature, is worthy of supporting: packets that are larger than one-mbuf size will be dropped in vhost worker's handle_rx if mrg_rxbuf feature is not used, but large packets cannot be avoided and increasing mbuf's size is not economical. With this virtio feature enabled by virtio-user, packet sockets with hardcoded 10-byte virtio net header will parse mac head incorrectly in packet_snd by taking the last two bytes of virtio net header as part of mac header. This incorrect mac header parsing will cause packet to be dropped due to invalid ether head checking in later under-layer device packet receiving. By adding extra field vnet_hdr_sz with utilizing holes in struct packet_sock to record currently used virtio net header size and supporting extra sockopt PACKET_VNET_HDR_SZ to set specified vnet_hdr_sz, packet sockets can know the exact length of virtio net header that virtio user gives. In packet_snd, tpacket_snd and packet_recvmsg, instead of using hardcoded virtio net header size, it can get the exact vnet_hdr_sz from corresponding packet_sock, and parse mac header correctly based on this information to avoid the packets being mistakenly dropped. Signed-off-by: Jianfeng Tan <henry.tjf@antgroup.com> Co-developed-by: Anqi Shen <amy.saq@antgroup.com> Signed-off-by: Anqi Shen <amy.saq@antgroup.com> Reviewed-by: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
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| samples | ||
| scripts | ||
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| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
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| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
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| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.