Add the IFF_BACKPRESSURE flag to the UAPI header and to its tools/ copy.
The flag has no effect yet, it is the opt-in switch for the qdisc
backpressure logic added by the following patches.
It is added to TUN_FEATURES only in the last patch of the series, once the
implementation is complete. Until then TUNSETIFF silently masks it off, as
it does for any flag outside TUN_FEATURES.
Keeping the flag and its users in separate patches would either leave a
window where backpressure is unconditional, or make the opt-in a later
add-on. Adding the flag first lets every following patch be a no-op
unless it is set.
Signed-off-by: Simon Schippers <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
There is a regular need in the kernel to provide a way to declare
having a dynamically sized set of trailing elements in a structure.
Kernel code should always use “flexible array members”[1] for these
cases. The older style of one-element or zero-length arrays should
no longer be used[2].
This code was transformed with the help of Coccinelle:
(linux-5.19-rc2$ spatch --jobs $(getconf _NPROCESSORS_ONLN) --sp-file script.cocci --include-headers --dir . > output.patch)
@@
identifier S, member, array;
type T1, T2;
@@
struct S {
...
T1 member;
T2 array[
- 0
];
};
-fstrict-flex-arrays=3 is coming and we need to land these changes
to prevent issues like these in the short future:
../fs/minix/dir.c:337:3: warning: 'strcpy' will always overflow; destination buffer has size 0,
but the source string has length 2 (including NUL byte) [-Wfortify-source]
strcpy(de3->name, ".");
^
Since these are all [0] to [] changes, the risk to UAPI is nearly zero. If
this breaks anything, we can use a union with a new member name.
[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays
Link: https://github.com/KSPP/linux/issues/78
Build-tested-by: kernel test robot <[email protected]>
Link: https://lore.kernel.org/lkml/62b675ec.wKX6AOZ6cbE71vtF%[email protected]/
Acked-by: Dan Williams <[email protected]> # For ndctl.h
Signed-off-by: Gustavo A. R. Silva <[email protected]>
When building the tools/testing/selftest/bpf subdirectory,
(running both a local directory "make" and a
"make -C tools/testing/selftests/bpf") I keep hitting the
following compilation error:
prog_tests/flow_dissector.c: In function ‘create_tap’:
prog_tests/flow_dissector.c:150:38: error: ‘IFF_NAPI’ undeclared (first
use in this function)
.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_NAPI | IFF_NAPI_FRAGS,
^
prog_tests/flow_dissector.c:150:38: note: each undeclared identifier is
reported only once for each function it appears in
prog_tests/flow_dissector.c:150:49: error: ‘IFF_NAPI_FRAGS’ undeclared
Adding include/uapi/linux/if_tun.h to tools/include/uapi/linux
resolves the problem and ensures the compilation of the file
does not depend on having up-to-date kernel headers locally.
Signed-off-by: Alan Maguire <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Simon Schippers