lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <CAF=yD-+tZ7xaU0rKWBuVbfdVWptj88Z=Xf4Mqx+zaC-gZ1U1mw@mail.gmail.com> Date: Mon, 6 Nov 2023 20:23:28 -0600 From: Willem de Bruijn <willemdebruijn.kernel@...il.com> To: Stanislav Fomichev <sdf@...gle.com> Cc: Mina Almasry <almasrymina@...gle.com>, David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, linux-kselftest@...r.kernel.org, linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Jesper Dangaard Brouer <hawk@...nel.org>, Ilias Apalodimas <ilias.apalodimas@...aro.org>, Arnd Bergmann <arnd@...db.de>, Shuah Khan <shuah@...nel.org>, Sumit Semwal <sumit.semwal@...aro.org>, Christian König <christian.koenig@....com>, Shakeel Butt <shakeelb@...gle.com>, Jeroen de Borst <jeroendb@...gle.com>, Praveen Kaligineedi <pkaligineedi@...gle.com>, Willem de Bruijn <willemb@...gle.com>, Kaiyuan Zhang <kaiyuanz@...gle.com> Subject: Re: [RFC PATCH v3 09/12] net: add support for skbs with unreadable frags > > > > I think my other issue with MSG_SOCK_DEVMEM being on recvmsg is that > > > > it somehow implies that I have an option of passing or not passing it > > > > for an individual system call. > > > > If we know that we're going to use dmabuf with the socket, maybe we > > > > should move this flag to the socket() syscall? > > > > > > > > fd = socket(AF_INET6, SOCK_STREAM, SOCK_DEVMEM); > > > > > > > > ? > > > > > > I think it should then be a setsockopt called before any data is > > > exchanged, with no change of modifying mode later. We generally use > > > setsockopts for the mode of a socket. This use of the protocol field > > > in socket() for setting a mode would be novel. Also, it might miss > > > passively opened connections, or be overly restrictive: one approach > > > for all accepted child sockets. > > > > I was thinking this is similar to SOCK_CLOEXEC or SOCK_NONBLOCK? There > > are plenty of bits we can grab. But setsockopt works as well! > > To follow up: if we have this flag on a socket, not on a per-message > basis, can we also use recvmsg for the recycling part maybe? > > while (true) { > memset(msg, 0, ...); > > /* receive the tokens */ > ret = recvmsg(fd, &msg, 0); > > /* recycle the tokens from the above recvmsg() */ > ret = recvmsg(fd, &msg, MSG_RECYCLE); > } > > recvmsg + MSG_RECYCLE can parse the same format that regular recvmsg > exports (SO_DEVMEM_OFFSET) and we can also add extra cmsg option > to recycle a range. > > Will this be more straightforward than a setsockopt(SO_DEVMEM_DONTNEED)? > Or is it more confusing? It would have to be sendmsg, as recvmsg is a copy_to_user operation. I am not aware of any precedent in multiplexing the data stream and a control operation stream in this manner. It would also require adding a branch in the sendmsg hot path. The memory is associated with the socket, freed when the socket is closed as well as on SO_DEVMEM_DONTNEED. Fundamentally it is a socket state operation, for which setsockopt is the socket interface. Is your request purely a dislike, or is there some technical concern with BPF and setsockopt?
Powered by blists - more mailing lists