diff options
| author | Simon Schippers <simon.schippers@tu-dortmund.de> | 2026-08-03 20:36:37 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-08-07 17:29:15 -0700 |
| commit | 485e38995cc3b39f1aa91c1d340cc66affcea39a (patch) | |
| tree | b5bf853d05e4b4158bdfeeb737f58f83be955b8b /tools/include | |
| parent | d4e359b3608a0e184bbe8d61a5c3b50d0831c44a (diff) | |
tun/tap: add IFF_BACKPRESSURE flag
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 <simon.schippers@tu-dortmund.de>
Link: https://patch.msgid.link/20260803183641.96882-2-simon.schippers@tu-dortmund.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'tools/include')
| -rw-r--r-- | tools/include/uapi/linux/if_tun.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/tools/include/uapi/linux/if_tun.h b/tools/include/uapi/linux/if_tun.h index 2ec07de1d73b..2c85525704c1 100644 --- a/tools/include/uapi/linux/if_tun.h +++ b/tools/include/uapi/linux/if_tun.h @@ -67,6 +67,10 @@ #define IFF_TAP 0x0002 #define IFF_NAPI 0x0010 #define IFF_NAPI_FRAGS 0x0020 +/* Stop the queue instead of dropping when the internal ring is full, so an + * attached qdisc applies backpressure instead of being bypassed. + */ +#define IFF_BACKPRESSURE 0x0080 #define IFF_NO_PI 0x1000 /* This flag has no real effect */ #define IFF_ONE_QUEUE 0x2000 |