From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Mack Subject: [PATCH v3 3/6] bpf: add BPF_PROG_ATTACH and BPF_PROG_DETACH commands Date: Fri, 26 Aug 2016 21:58:49 +0200 Message-ID: <1472241532-11682-4-git-send-email-daniel@zonque.org> References: <1472241532-11682-1-git-send-email-daniel@zonque.org> Cc: davem@davemloft.net, kafai@fb.com, fw@strlen.de, pablo@netfilter.org, harald@redhat.com, netdev@vger.kernel.org, sargun@sargun.me, Daniel Mack To: htejun@fb.com, daniel@iogearbox.net, ast@fb.com Return-path: Received: from svenfoo.org ([82.94.215.22]:37907 "EHLO mail.zonque.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753037AbcHZT7D (ORCPT ); Fri, 26 Aug 2016 15:59:03 -0400 In-Reply-To: <1472241532-11682-1-git-send-email-daniel@zonque.org> Sender: netdev-owner@vger.kernel.org List-ID: Extend the bpf(2) syscall by two new commands, BPF_PROG_ATTACH and BPF_PROG_DETACH which allow attaching and detaching eBPF programs to a target. On the API level, the target could be anything that has an fd in userspace, hence the name of the field in union bpf_attr is called 'target_fd'. When called with BPF_ATTACH_TYPE_CGROUP_INET_{E,IN}GRESS, the target is expected to be a valid file descriptor of a cgroup v2 directory which has the bpf controller enabled. These are the only use-cases implemented by this patch at this point, but more can be added. If a program of the given type already exists in the given cgroup, the program is swapped automically, so userspace does not have to drop an existing program first before installing a new one, which would otherwise leave a gap in which no program is attached. For more information on the propagation logic to subcgroups, please refer to the bpf cgroup controller implementation. The API is guarded by CAP_NET_ADMIN. Signed-off-by: Daniel Mack syscall --- include/uapi/linux/bpf.h | 9 ++++++ kernel/bpf/syscall.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 92 insertions(+) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 1d5db42..4cc2dcf 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -73,6 +73,8 @@ enum bpf_cmd { BPF_PROG_LOAD, BPF_OBJ_PIN, BPF_OBJ_GET, + BPF_PROG_ATTACH, + BPF_PROG_DETACH, }; enum bpf_map_type { @@ -147,6 +149,13 @@ union bpf_attr { __aligned_u64 pathname; __u32 bpf_fd; }; + + struct { /* anonymous struct used by BPF_PROG_ATTACH/DETACH commands */ + __u32 target_fd; /* container object to attach to */ + __u32 attach_bpf_fd; /* eBPF program to attach */ + __u32 attach_type; /* BPF_ATTACH_TYPE_* */ + __u64 attach_flags; + }; } __attribute__((aligned(8))); /* integer value in 'imm' field of BPF_CALL instruction selects which helper diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 228f962..cc4d603 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -822,6 +822,79 @@ static int bpf_obj_get(const union bpf_attr *attr) return bpf_obj_get_user(u64_to_ptr(attr->pathname)); } +#ifdef CONFIG_CGROUP_BPF +static int bpf_prog_attach(const union bpf_attr *attr) +{ + struct bpf_prog *prog; + + if (!capable(CAP_NET_ADMIN)) + return -EPERM; + + /* Flags are unused for now */ + if (attr->attach_flags != 0) + return -EINVAL; + + switch (attr->attach_type) { + case BPF_ATTACH_TYPE_CGROUP_INET_INGRESS: + case BPF_ATTACH_TYPE_CGROUP_INET_EGRESS: { + struct cgroup *cgrp; + + prog = bpf_prog_get_type(attr->attach_bpf_fd, + BPF_PROG_TYPE_CGROUP_SOCKET_FILTER); + if (IS_ERR(prog)) + return PTR_ERR(prog); + + cgrp = cgroup_get_from_fd(attr->target_fd); + if (IS_ERR(cgrp)) { + bpf_prog_put(prog); + return PTR_ERR(cgrp); + } + + cgroup_bpf_update(cgrp, prog, attr->attach_type); + cgroup_put(cgrp); + + break; + } + + default: + return -EINVAL; + } + + return 0; +} + +static int bpf_prog_detach(const union bpf_attr *attr) +{ + if (!capable(CAP_NET_ADMIN)) + return -EPERM; + + /* Flags are unused for now */ + if (attr->attach_flags != 0) + return -EINVAL; + + switch (attr->attach_type) { + case BPF_ATTACH_TYPE_CGROUP_INET_INGRESS: + case BPF_ATTACH_TYPE_CGROUP_INET_EGRESS: { + struct cgroup *cgrp; + + cgrp = cgroup_get_from_fd(attr->target_fd); + if (IS_ERR(cgrp)) + return PTR_ERR(cgrp); + + cgroup_bpf_update(cgrp, NULL, attr->attach_type); + cgroup_put(cgrp); + + break; + } + + default: + return -EINVAL; + } + + return 0; +} +#endif /* CONFIG_CGROUP_BPF */ + SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size) { union bpf_attr attr = {}; @@ -888,6 +961,16 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz case BPF_OBJ_GET: err = bpf_obj_get(&attr); break; + +#ifdef CONFIG_CGROUP_BPF + case BPF_PROG_ATTACH: + err = bpf_prog_attach(&attr); + break; + case BPF_PROG_DETACH: + err = bpf_prog_detach(&attr); + break; +#endif + default: err = -EINVAL; break; -- 2.5.5