> From: Thomas Monjalon [mailto:tho...@monjalon.net] > Sent: Friday, 6 August 2021 16.21 > > 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/ >
Perfect! Thanks. -Morten
