Messages in this thread | | | Date | Tue, 1 Mar 2022 16:25:21 +0100 | From | Samuel Thibault <> | Subject | Re: [PATCH] SO_ZEROCOPY should rather return -ENOPROTOOPT |
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Willem de Bruijn, le mar. 01 mars 2022 10:21:41 -0500, a ecrit: > On Tue, Mar 1, 2022 at 10:20 AM Samuel Thibault > <samuel.thibault@labri.fr> wrote: > > > > Willem de Bruijn, le mar. 01 mars 2022 10:14:18 -0500, a ecrit: > > > On Tue, Mar 1, 2022 at 10:00 AM Samuel Thibault > > > <samuel.thibault@labri.fr> wrote: > > > > > > > > Willem de Bruijn, le mar. 01 mars 2022 09:51:45 -0500, a ecrit: > > > > > On Tue, Mar 1, 2022 at 9:44 AM Samuel Thibault <samuel.thibault@labri.fr> wrote: > > > > > > > > > > > > ENOTSUPP is documented as "should never be seen by user programs", and > > > > > > is not exposed in <errno.h>, so applications cannot safely check against > > > > > > it. We should rather return the well-known -ENOPROTOOPT. > > > > > > > > > > > > Signed-off-by: Samuel Thibault <samuel.thibault@labri.fr> > > > > > > > > > > > > diff --git a/net/core/sock.c b/net/core/sock.c > > > > > > index 4ff806d71921..6e5b84194d56 100644 > > > > > > --- a/net/core/sock.c > > > > > > +++ b/net/core/sock.c > > > > > > @@ -1377,9 +1377,9 @@ int sock_setsockopt(struct socket *sock, int level, int optname, > > > > > > if (!(sk_is_tcp(sk) || > > > > > > (sk->sk_type == SOCK_DGRAM && > > > > > > sk->sk_protocol == IPPROTO_UDP))) > > > > > > - ret = -ENOTSUPP; > > > > > > + ret = -ENOPROTOOPT; > > > > > > } else if (sk->sk_family != PF_RDS) { > > > > > > - ret = -ENOTSUPP; > > > > > > + ret = -ENOPROTOOPT; > > > > > > } > > > > > > if (!ret) { > > > > > > if (val < 0 || val > 1) > > > > > > > > > > That should have been a public error code. Perhaps rather EOPNOTSUPP. > > > > > > > > > > The problem with a change now is that it will confuse existing > > > > > applications that check for -524 (ENOTSUPP). > > > > > > > > They were not supposed to hardcord -524... > > > > > > > > Actually, they already had to check against EOPNOTSUPP to support older > > > > kernels, so EOPNOTSUPP is not supposed to pose a problem. > > > > > > Which older kernels returned EOPNOTSUPP on SO_ZEROCOPY? > > > > Sorry, bad copy/paste, I meant ENOPROTOOPT. > > Same point though, right? These are not legacy concerns, but specific > to applications written to SO_ZEROCOPY. > > I expect that most will just ignore the exact error code and will work > with either.
Well, in the code I just wrote, I ignored ENOPROTOOPT due to older kernels, and it's only when the code happened to be run against PF_LOCAL sockets that the ENOTSUPP question raised. My code has never been exposed to a EOPNOTSUPP error, so I would have never written a check against EOPNOTSUPP if you didn't mention it as a possibility.
Samuel
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