05/08/2021 08:08, Morten Brørup: > > From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Thomas Monjalon > > Sent: Wednesday, 4 August 2021 15.30 > > > > A bug with segmented packets has been discovered but the agreement > > to apply the fix is not concluded at the time of DPDK 21.08 release. > > This bug seems to be in DPDK for many years and should be fixed in > > 21.11. > > > > Suggested-by: Olivier Matz <olivier.m...@6wind.com> > > Signed-off-by: Thomas Monjalon <tho...@monjalon.net> > > --- > > doc/guides/rel_notes/release_21_08.rst | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/doc/guides/rel_notes/release_21_08.rst > > b/doc/guides/rel_notes/release_21_08.rst > > index d7559ec6bf..14e32585b8 100644 > > --- a/doc/guides/rel_notes/release_21_08.rst > > +++ b/doc/guides/rel_notes/release_21_08.rst > > @@ -251,6 +251,18 @@ Known Issues > > Also, make sure to start the actual text at the margin. > > ======================================================= > > > > +* **Last mbuf segment not implicitly reset.** > > + > > + It is expected that free mbufs have their field ``nb_seg`` set to 1, > > + so that when it is allocated, the user does not need to set its > > value. > > + The mbuf free functions are responsible of resetting this field to 1 > > + before returning the mbuf to the pool. > > + > > + When a multi-segment mbuf is freed, the field ``nb_seg`` is not > > reset > > + to 1 for the last segment of the chain. On next allocation of this > > segment, > > + if the field is not explicitly reset by the user, > > + an invalid mbuf can be created, and can cause an undefined behavior. > > + > > > > I have a couple of suggestions: > > 1. Add that this bug was present in previous DPDK releases for many years. If > possible, mention which release introduced the bug. > > We don't want users to choose to stay on older release, thinking that it does > not have this bug. > > Also, if a user experiences unexplainable problems with segmented packets an > older DPDK release, he might get lucky and find these release notes, which > could reveal the root cause of the problems he is experiencing. > > 2. Add a link to the patch that fixes the bug. It will let users affected by > the bug easily fix it (possibly at the expense of degraded performance). > > With those two additions, > Acked-by: Morten Brørup <m...@smartsharesystems.com>
Applied with the suggested additions: + This issue has a root cause in DPDK 17.05, meaning it is 4 years old. + A fix is available and discussed but not merged in DPDK 21.08: + https://patches.dpdk.org/patch/86458/
