Linux kernel modifications for the Kernel Hacking exam
2b272bb558
When using a xfrm interface in a bridged setup (the outgoing device is
bridged), the incoming packets in the xfrm interface are only tracked
in the outgoing direction.
$ brctl show
bridge name interfaces
br_eth1 eth1
$ conntrack -L
tcp 115 SYN_SENT src=192... dst=192... [UNREPLIED] ...
If br_netfilter is enabled, the first (encrypted) packet is received onR
eth1, conntrack hooks are called from br_netfilter emulation which
allocates nf_bridge info for this skb.
If the packet is for local machine, skb gets passed up the ip stack.
The skb passes through ip prerouting a second time. br_netfilter
ip_sabotage_in supresses the re-invocation of the hooks.
After this, skb gets decrypted in xfrm layer and appears in
network stack a second time (after decryption).
Then, ip_sabotage_in is called again and suppresses netfilter
hook invocation, even though the bridge layer never called them
for the plaintext incarnation of the packet.
Free the bridge info after the first suppression to avoid this.
I was unable to figure out where the regression comes from, as far as i
can see br_netfilter always had this problem; i did not expect that skb
is looped again with different headers.
Fixes:
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||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| 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.