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Message-ID: <3e4e33c19a9c608be863d2d7207f5a9cb7db795f.camel@redhat.com> Date: Tue, 28 Mar 2023 14:14:59 -0400 From: Jeff Layton <jlayton@...hat.com> To: Chuck Lever <cel@...nel.org>, kuba@...nel.org, pabeni@...hat.com, edumazet@...gle.com Cc: netdev@...r.kernel.org, kernel-tls-handshake@...ts.linux.dev, john.haxby@...cle.com Subject: Re: [PATCH v7 1/2] net/handshake: Create a NETLINK service for handling handshake requests On Sat, 2023-03-18 at 12:18 -0400, Chuck Lever wrote: > From: Chuck Lever <chuck.lever@...cle.com> > > When a kernel consumer needs a transport layer security session, it > first needs a handshake to negotiate and establish a session. This > negotiation can be done in user space via one of the several > existing library implementations, or it can be done in the kernel. > > No in-kernel handshake implementations yet exist. In their absence, > we add a netlink service that can: > > a. Notify a user space daemon that a handshake is needed. > > b. Once notified, the daemon calls the kernel back via this > netlink service to get the handshake parameters, including an > open socket on which to establish the session. > > c. Once the handshake is complete, the daemon reports the > session status and other information via a second netlink > operation. This operation marks that it is safe for the > kernel to use the open socket and the security session > established there. > > The notification service uses a multicast group. Each handshake > mechanism (eg, tlshd) adopts its own group number so that the > handshake services are completely independent of one another. The > kernel can then tell via netlink_has_listeners() whether a handshake > service is active and prepared to handle a handshake request. > > A new netlink operation, ACCEPT, acts like accept(2) in that it > instantiates a file descriptor in the user space daemon's fd table. > If this operation is successful, the reply carries the fd number, > which can be treated as an open and ready file descriptor. > > While user space is performing the handshake, the kernel keeps its > muddy paws off the open socket. A second new netlink operation, > DONE, indicates that the user space daemon is finished with the > socket and it is safe for the kernel to use again. The operation > also indicates whether a session was established successfully. > > Signed-off-by: Chuck Lever <chuck.lever@...cle.com> > --- > Documentation/netlink/specs/handshake.yaml | 122 +++++++++++ > MAINTAINERS | 8 + > include/trace/events/handshake.h | 159 ++++++++++++++ > include/uapi/linux/handshake.h | 70 ++++++ > net/Kconfig | 5 > net/Makefile | 1 > net/handshake/Makefile | 11 + > net/handshake/genl.c | 57 +++++ > net/handshake/genl.h | 23 ++ > net/handshake/handshake.h | 82 +++++++ > net/handshake/netlink.c | 316 ++++++++++++++++++++++++++++ > net/handshake/request.c | 307 +++++++++++++++++++++++++++ > net/handshake/trace.c | 20 ++ > 13 files changed, 1181 insertions(+) > create mode 100644 Documentation/netlink/specs/handshake.yaml > create mode 100644 include/trace/events/handshake.h > create mode 100644 include/uapi/linux/handshake.h > create mode 100644 net/handshake/Makefile > create mode 100644 net/handshake/genl.c > create mode 100644 net/handshake/genl.h > create mode 100644 net/handshake/handshake.h > create mode 100644 net/handshake/netlink.c > create mode 100644 net/handshake/request.c > create mode 100644 net/handshake/trace.c > > [...] > diff --git a/net/handshake/request.c b/net/handshake/request.c > new file mode 100644 > index 000000000000..3f8ae9e990d2 > --- /dev/null > +++ b/net/handshake/request.c > @@ -0,0 +1,307 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Handshake request lifetime events > + * > + * Author: Chuck Lever <chuck.lever@...cle.com> > + * > + * Copyright (c) 2023, Oracle and/or its affiliates. > + */ > + > +#include <linux/types.h> > +#include <linux/socket.h> > +#include <linux/kernel.h> > +#include <linux/module.h> > +#include <linux/skbuff.h> > +#include <linux/inet.h> > +#include <linux/fdtable.h> > +#include <linux/rhashtable.h> > + > +#include <net/sock.h> > +#include <net/genetlink.h> > +#include <net/netns/generic.h> > + > +#include <uapi/linux/handshake.h> > +#include "handshake.h" > + > +#include <trace/events/handshake.h> > + > +/* > + * We need both a handshake_req -> sock mapping, and a sock -> > + * handshake_req mapping. Both are one-to-one. > + * > + * To avoid adding another pointer field to struct sock, net/handshake > + * maintains a hash table, indexed by the memory address of @sock, to > + * find the struct handshake_req outstanding for that socket. The > + * reverse direction uses a simple pointer field in the handshake_req > + * struct. > + */ > + > +static struct rhashtable handshake_rhashtbl ____cacheline_aligned_in_smp; > + > +static const struct rhashtable_params handshake_rhash_params = { > + .key_len = sizeof_field(struct handshake_req, hr_sk), > + .key_offset = offsetof(struct handshake_req, hr_sk), > + .head_offset = offsetof(struct handshake_req, hr_rhash), > + .automatic_shrinking = true, > +}; > + > +int handshake_req_hash_init(void) > +{ > + return rhashtable_init(&handshake_rhashtbl, &handshake_rhash_params); > +} > + > +void handshake_req_hash_destroy(void) > +{ > + rhashtable_destroy(&handshake_rhashtbl); > +} > + > +struct handshake_req *handshake_req_hash_lookup(struct sock *sk) > +{ > + return rhashtable_lookup_fast(&handshake_rhashtbl, &sk, Is this correct? It seems like we should be searching for the struct sock pointer value, not on the pointer to the pointer (which will be a stack var), right? > + handshake_rhash_params); > +} > + > +static noinline bool handshake_req_hash_add(struct handshake_req *req) > +{ > + int ret; > + > + ret = rhashtable_lookup_insert_fast(&handshake_rhashtbl, > + &req->hr_rhash, > + handshake_rhash_params); > + return ret == 0; > +} > + > +static noinline void handshake_req_destroy(struct handshake_req *req) > +{ > + if (req->hr_proto->hp_destroy) > + req->hr_proto->hp_destroy(req); > + rhashtable_remove_fast(&handshake_rhashtbl, &req->hr_rhash, > + handshake_rhash_params); > + kfree(req); > +} > + > +static void handshake_sk_destruct(struct sock *sk) > +{ > + void (*sk_destruct)(struct sock *sk); > + struct handshake_req *req; > + > + req = handshake_req_hash_lookup(sk); > + if (!req) > + return; > + > + trace_handshake_destruct(sock_net(sk), req, sk); > + sk_destruct = req->hr_odestruct; > + handshake_req_destroy(req); > + if (sk_destruct) > + sk_destruct(sk); > +} > + > +/** > + * handshake_req_alloc - consumer API to allocate a request > + * @sock: open socket on which to perform a handshake > + * @proto: security protocol > + * @flags: memory allocation flags > + * > + * Returns an initialized handshake_req or NULL. > + */ > +struct handshake_req *handshake_req_alloc(struct socket *sock, > + const struct handshake_proto *proto, > + gfp_t flags) > +{ > + struct sock *sk = sock->sk; > + struct net *net = sock_net(sk); > + struct handshake_net *hn = handshake_pernet(net); > + struct handshake_req *req; > + > + if (!hn) > + return NULL; > + > + req = kzalloc(struct_size(req, hr_priv, proto->hp_privsize), flags); > + if (!req) > + return NULL; > + > + sock_hold(sk); > + > + INIT_LIST_HEAD(&req->hr_list); > + req->hr_sk = sk; > + req->hr_proto = proto; > + return req; > +} > +EXPORT_SYMBOL(handshake_req_alloc); > + > +/** > + * handshake_req_private - consumer API to return per-handshake private data > + * @req: handshake arguments > + * > + */ > +void *handshake_req_private(struct handshake_req *req) > +{ > + return (void *)&req->hr_priv; > +} > +EXPORT_SYMBOL(handshake_req_private); > + > +static bool __add_pending_locked(struct handshake_net *hn, > + struct handshake_req *req) > +{ > + if (!list_empty(&req->hr_list)) > + return false; > + hn->hn_pending++; > + list_add_tail(&req->hr_list, &hn->hn_requests); > + return true; > +} > + > +void __remove_pending_locked(struct handshake_net *hn, > + struct handshake_req *req) > +{ > + hn->hn_pending--; > + list_del_init(&req->hr_list); > +} > + > +/* > + * Returns %true if the request was found on @net's pending list, > + * otherwise %false. > + * > + * If @req was on a pending list, it has not yet been accepted. > + */ > +static bool remove_pending(struct handshake_net *hn, struct handshake_req *req) > +{ > + bool ret; > + > + ret = false; > + > + spin_lock(&hn->hn_lock); > + if (!list_empty(&req->hr_list)) { > + __remove_pending_locked(hn, req); > + ret = true; > + } > + spin_unlock(&hn->hn_lock); > + > + return ret; > +} > + > +/** > + * handshake_req_submit - consumer API to submit a handshake request > + * @req: handshake arguments > + * @flags: memory allocation flags > + * > + * Return values: > + * %0: Request queued > + * %-EBUSY: A handshake is already under way for this socket > + * %-ESRCH: No handshake agent is available > + * %-EAGAIN: Too many pending handshake requests > + * %-ENOMEM: Failed to allocate memory > + * %-EMSGSIZE: Failed to construct notification message > + * %-EOPNOTSUPP: Handshake module not initialized > + * > + * A zero return value from handshake_request() means that > + * exactly one subsequent completion callback is guaranteed. > + * > + * A negative return value from handshake_request() means that > + * no completion callback will be done and that @req has been > + * destroyed. > + */ > +int handshake_req_submit(struct handshake_req *req, gfp_t flags) > +{ > + struct sock *sk = req->hr_sk; > + struct net *net = sock_net(sk); > + struct handshake_net *hn = handshake_pernet(net); > + int ret; > + > + if (!hn) > + return -EOPNOTSUPP; > + > + ret = -EAGAIN; > + if (READ_ONCE(hn->hn_pending) >= hn->hn_pending_max) > + goto out_err; > + > + req->hr_odestruct = sk->sk_destruct; > + sk->sk_destruct = handshake_sk_destruct; > + spin_lock(&hn->hn_lock); > + ret = -EOPNOTSUPP; > + if (test_bit(HANDSHAKE_F_NET_DRAINING, &hn->hn_flags)) > + goto out_unlock; > + ret = -EBUSY; > + if (!handshake_req_hash_add(req)) > + goto out_unlock; > + if (!__add_pending_locked(hn, req)) > + goto out_unlock; > + spin_unlock(&hn->hn_lock); > + > + ret = handshake_genl_notify(net, req->hr_proto->hp_handler_class, > + flags); > + if (ret) { > + trace_handshake_notify_err(net, req, sk, ret); > + if (remove_pending(hn, req)) > + goto out_err; > + } > + > + trace_handshake_submit(net, req, sk); > + return 0; > + > +out_unlock: > + spin_unlock(&hn->hn_lock); > +out_err: > + trace_handshake_submit_err(net, req, sk, ret); > + handshake_req_destroy(req); > + return ret; > +} > +EXPORT_SYMBOL(handshake_req_submit); > + > +void handshake_complete(struct handshake_req *req, unsigned int status, > + struct genl_info *info) > +{ > + struct sock *sk = req->hr_sk; > + struct net *net = sock_net(sk); > + > + if (!test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED, &req->hr_flags)) { > + trace_handshake_complete(net, req, sk, status); > + req->hr_proto->hp_done(req, status, info); > + __sock_put(sk); > + } > +} > + > +/** > + * handshake_req_cancel - consumer API to cancel an in-progress handshake > + * @sock: socket on which there is an ongoing handshake > + * > + * XXX: Perhaps killing the user space agent might also be necessary? > + * > + * Request cancellation races with request completion. To determine > + * who won, callers examine the return value from this function. > + * > + * Return values: > + * %true - Uncompleted handshake request was canceled or not found > + * %false - Handshake request already completed > + */ > +bool handshake_req_cancel(struct socket *sock) > +{ > + struct handshake_req *req; > + struct handshake_net *hn; > + struct sock *sk; > + struct net *net; > + > + sk = sock->sk; > + net = sock_net(sk); > + req = handshake_req_hash_lookup(sk); > + if (!req) { > + trace_handshake_cancel_none(net, req, sk); > + return true; > + } > + > + hn = handshake_pernet(net); > + if (hn && remove_pending(hn, req)) { > + /* Request hadn't been accepted */ > + trace_handshake_cancel(net, req, sk); > + return true; > + } > + if (test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED, &req->hr_flags)) { > + /* Request already completed */ > + trace_handshake_cancel_busy(net, req, sk); > + return false; > + } > + > + __sock_put(sk); > + trace_handshake_cancel(net, req, sk); > + return true; > +} > +EXPORT_SYMBOL(handshake_req_cancel); > diff --git a/net/handshake/trace.c b/net/handshake/trace.c > new file mode 100644 > index 000000000000..1c4d8e27e17a > --- /dev/null > +++ b/net/handshake/trace.c > @@ -0,0 +1,20 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Trace points for transport security layer handshakes. > + * > + * Author: Chuck Lever <chuck.lever@...cle.com> > + * > + * Copyright (c) 2023, Oracle and/or its affiliates. > + */ > + > +#include <linux/types.h> > + > +#include <net/sock.h> > +#include <net/netlink.h> > +#include <net/genetlink.h> > + > +#include "handshake.h" > + > +#define CREATE_TRACE_POINTS > + > +#include <trace/events/handshake.h> > > > -- Jeff Layton <jlayton@...hat.com>
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