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21c5f4f55d
Linux 5.1 implemented 64-bit time types and related syscalls to address the
Y2038 problem generally across archs. Userspace handling of Y2038 varies
with the libc however. While musl libc uses 64-bit time across all 32-bit
and 64-bit platforms, GNU glibc uses 64-bit time on 64-bit platforms but
defaults to 32-bit time on 32-bit platforms unless they "opt-in" to 64-bit
time or explicitly use 64-bit syscalls and time structures.
One specific area is the standard setsockopt() call, SO_TIMESTAMPNS option
used for timestamping, and the related output 'struct timespec'. GNU glibc
defaults as above, also exposing the SO_TIMESTAMPNS_NEW flag to explicitly
use a 64-bit call and 'struct __kernel_timespec'. Since these are not
exposed or needed with musl libc, their use in tc_redirect.c leads to
compile errors building for mips64el/musl:
tc_redirect.c: In function 'rcv_tstamp':
tc_redirect.c:425:32: error: 'SO_TIMESTAMPNS_NEW' undeclared (first use in this function); did you mean 'SO_TIMESTAMPNS'?
425 | cmsg->cmsg_type == SO_TIMESTAMPNS_NEW)
| ^~~~~~~~~~~~~~~~~~
| SO_TIMESTAMPNS
tc_redirect.c:425:32: note: each undeclared identifier is reported only once for each function it appears in
tc_redirect.c: In function 'test_inet_dtime':
tc_redirect.c:491:49: error: 'SO_TIMESTAMPNS_NEW' undeclared (first use in this function); did you mean 'SO_TIMESTAMPNS'?
491 | err = setsockopt(listen_fd, SOL_SOCKET, SO_TIMESTAMPNS_NEW,
| ^~~~~~~~~~~~~~~~~~
| SO_TIMESTAMPNS
However, using SO_TIMESTAMPNS_NEW isn't strictly needed, nor is Y2038 being
explicitly tested. The timestamp checks in tc_redirect.c are simple: the
packet receive timestamp is non-zero and processed/handled in less than 5
seconds.
Switch to using the standard setsockopt() call and SO_TIMESTAMPNS option to
ensure compatibility across glibc and musl libc. In the worst-case, there
is a 5-second window 14 years from now where tc_redirect tests may fail on
32-bit systems. However, we should reasonably expect glibc to adopt a
64-bit mandate rather than the current "opt-in" policy before the Y2038
roll-over.
Fixes:
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History
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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.