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Jiayuan Chen says: ==================== tcp: add a new TW_PAWS drop reason Devices in the networking path, such as firewalls, NATs, or routers, which can perform SNAT or DNAT, use addresses from their own limited address pools to masquerade the source address during forwarding, causing PAWS verification to fail more easily under TW status. Currently, packet loss statistics for PAWS can only be viewed through MIB, which is a global metric and cannot be precisely obtained through tracing to get the specific 4-tuple of the dropped packet. In the past, we had to use kprobe ret to retrieve relevant skb information from tcp_timewait_state_process(). We add a drop_reason pointer and a new counter. I didn't provide a packetdrill script. I struggled for a long time to get packetdrill to fix the client port, but ultimately failed to do so... Instead, I wrote my own program to trigger PAWS, which can be found at https://github.com/mrpre/nettrigger/tree/main ''' //assume nginx running on 172.31.75.114:9999, current host is 172.31.75.115 iptables -t filter -I OUTPUT -p tcp --sport 12345 --tcp-flags RST RST -j DROP ./nettrigger -i eth0 -s 172.31.75.115:12345 -d 172.31.75.114:9999 -action paws ''' v2: https://lore.kernel.org/5cdc1bdd9caee92a6ae932638a862fd5c67630e8@linux.dev v3: https://lore.kernel.org/20250407140001.13886-1-jiayuan.chen@linux.dev ==================== Link: https://patch.msgid.link/20250409112614.16153-1-jiayuan.chen@linux.dev Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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 reStructuredText 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.