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[209.132.180.67]) by mx.google.com with ESMTP id e26si13980685pfb.185.2018.05.03.07.25.04; Thu, 03 May 2018 07:25:18 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751359AbeECOYK (ORCPT + 99 others); Thu, 3 May 2018 10:24:10 -0400 Received: from dispatch1-us1.ppe-hosted.com ([67.231.154.164]:37592 "EHLO dispatch1-us1.ppe-hosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751137AbeECOYH (ORCPT ); Thu, 3 May 2018 10:24:07 -0400 X-Virus-Scanned: Proofpoint Essentials engine Received: from webmail.solarflare.com (webmail.solarflare.com [12.187.104.26]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1-us3.ppe-hosted.com (Proofpoint Essentials ESMTP Server) with ESMTPS id DBD21980067; Thu, 3 May 2018 14:24:01 +0000 (UTC) Received: from ec-desktop.uk.solarflarecom.com (10.17.20.45) by ocex03.SolarFlarecom.com (10.20.40.36) with Microsoft SMTP Server (TLS) id 15.0.1044.25; Thu, 3 May 2018 07:23:56 -0700 Subject: Re: [PATCH v2 net-next 2/4] net: add skeleton of bpfilter kernel module To: Alexei Starovoitov , CC: , , , , , , References: <20180503043604.1604587-1-ast@kernel.org> <20180503043604.1604587-3-ast@kernel.org> From: Edward Cree Message-ID: Date: Thu, 3 May 2018 15:23:55 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <20180503043604.1604587-3-ast@kernel.org> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Content-Language: en-GB X-Originating-IP: [10.17.20.45] X-MDID: 1525357443-mGoY2g856LdY Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/05/18 05:36, Alexei Starovoitov wrote: > bpfilter.ko consists of bpfilter_kern.c (normal kernel module code) > and user mode helper code that is embedded into bpfilter.ko > > The steps to build bpfilter.ko are the following: > - main.c is compiled by HOSTCC into the bpfilter_umh elf executable file > - with quite a bit of objcopy and Makefile magic the bpfilter_umh elf file > is converted into bpfilter_umh.o object file > with _binary_net_bpfilter_bpfilter_umh_start and _end symbols > Example: > $ nm ./bld_x64/net/bpfilter/bpfilter_umh.o > 0000000000004cf8 T _binary_net_bpfilter_bpfilter_umh_end > 0000000000004cf8 A _binary_net_bpfilter_bpfilter_umh_size > 0000000000000000 T _binary_net_bpfilter_bpfilter_umh_start > - bpfilter_umh.o and bpfilter_kern.o are linked together into bpfilter.ko > > bpfilter_kern.c is a normal kernel module code that calls > the fork_usermode_blob() helper to execute part of its own data > as a user mode process. > > Notice that _binary_net_bpfilter_bpfilter_umh_start - end > is placed into .init.rodata section, so it's freed as soon as __init > function of bpfilter.ko is finished. > As part of __init the bpfilter.ko does first request/reply action > via two unix pipe provided by fork_usermode_blob() helper to > make sure that umh is healthy. If not it will kill it via pid. > > Later bpfilter_process_sockopt() will be called from bpfilter hooks > in get/setsockopt() to pass iptable commands into umh via bpfilter.ko > > If admin does 'rmmod bpfilter' the __exit code bpfilter.ko will > kill umh as well. > > Signed-off-by: Alexei Starovoitov > --- > include/linux/bpfilter.h | 15 +++++++ > include/uapi/linux/bpfilter.h | 21 ++++++++++ > net/Kconfig | 2 + > net/Makefile | 1 + > net/bpfilter/Kconfig | 17 ++++++++ > net/bpfilter/Makefile | 24 +++++++++++ > net/bpfilter/bpfilter_kern.c | 93 +++++++++++++++++++++++++++++++++++++++++++ > net/bpfilter/main.c | 63 +++++++++++++++++++++++++++++ > net/bpfilter/msgfmt.h | 17 ++++++++ > net/ipv4/Makefile | 2 + > net/ipv4/bpfilter/Makefile | 2 + > net/ipv4/bpfilter/sockopt.c | 42 +++++++++++++++++++ > net/ipv4/ip_sockglue.c | 17 ++++++++ > 13 files changed, 316 insertions(+) > create mode 100644 include/linux/bpfilter.h > create mode 100644 include/uapi/linux/bpfilter.h > create mode 100644 net/bpfilter/Kconfig > create mode 100644 net/bpfilter/Makefile > create mode 100644 net/bpfilter/bpfilter_kern.c > create mode 100644 net/bpfilter/main.c > create mode 100644 net/bpfilter/msgfmt.h > create mode 100644 net/ipv4/bpfilter/Makefile > create mode 100644 net/ipv4/bpfilter/sockopt.c > > diff --git a/include/linux/bpfilter.h b/include/linux/bpfilter.h > new file mode 100644 > index 000000000000..687b1760bb9f > --- /dev/null > +++ b/include/linux/bpfilter.h > @@ -0,0 +1,15 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _LINUX_BPFILTER_H > +#define _LINUX_BPFILTER_H > + > +#include > + > +struct sock; > +int bpfilter_ip_set_sockopt(struct sock *sk, int optname, char *optval, > + unsigned int optlen); > +int bpfilter_ip_get_sockopt(struct sock *sk, int optname, char *optval, > + int *optlen); > +extern int (*bpfilter_process_sockopt)(struct sock *sk, int optname, > + char __user *optval, > + unsigned int optlen, bool is_set); > +#endif > diff --git a/include/uapi/linux/bpfilter.h b/include/uapi/linux/bpfilter.h > new file mode 100644 > index 000000000000..2ec3cc99ea4c > --- /dev/null > +++ b/include/uapi/linux/bpfilter.h > @@ -0,0 +1,21 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _UAPI_LINUX_BPFILTER_H > +#define _UAPI_LINUX_BPFILTER_H > + > +#include > + > +enum { > + BPFILTER_IPT_SO_SET_REPLACE = 64, > + BPFILTER_IPT_SO_SET_ADD_COUNTERS = 65, > + BPFILTER_IPT_SET_MAX, > +}; > + > +enum { > + BPFILTER_IPT_SO_GET_INFO = 64, > + BPFILTER_IPT_SO_GET_ENTRIES = 65, > + BPFILTER_IPT_SO_GET_REVISION_MATCH = 66, > + BPFILTER_IPT_SO_GET_REVISION_TARGET = 67, > + BPFILTER_IPT_GET_MAX, > +}; > + > +#endif /* _UAPI_LINUX_BPFILTER_H */ > diff --git a/net/Kconfig b/net/Kconfig > index b62089fb1332..ed6368b306fa 100644 > --- a/net/Kconfig > +++ b/net/Kconfig > @@ -201,6 +201,8 @@ source "net/bridge/netfilter/Kconfig" > > endif > > +source "net/bpfilter/Kconfig" > + > source "net/dccp/Kconfig" > source "net/sctp/Kconfig" > source "net/rds/Kconfig" > diff --git a/net/Makefile b/net/Makefile > index a6147c61b174..7f982b7682bd 100644 > --- a/net/Makefile > +++ b/net/Makefile > @@ -20,6 +20,7 @@ obj-$(CONFIG_TLS) += tls/ > obj-$(CONFIG_XFRM) += xfrm/ > obj-$(CONFIG_UNIX) += unix/ > obj-$(CONFIG_NET) += ipv6/ > +obj-$(CONFIG_BPFILTER) += bpfilter/ > obj-$(CONFIG_PACKET) += packet/ > obj-$(CONFIG_NET_KEY) += key/ > obj-$(CONFIG_BRIDGE) += bridge/ > diff --git a/net/bpfilter/Kconfig b/net/bpfilter/Kconfig > new file mode 100644 > index 000000000000..782a732b9a5c > --- /dev/null > +++ b/net/bpfilter/Kconfig > @@ -0,0 +1,17 @@ > +menuconfig BPFILTER > + bool "BPF based packet filtering framework (BPFILTER)" > + default n > + depends on NET && BPF > + help > + This builds experimental bpfilter framework that is aiming to > + provide netfilter compatible functionality via BPF > + > +if BPFILTER > +config BPFILTER_UMH > + tristate "bpftiler kernel module with user mode helper" sp. "bpftiler" -> "bpfilter" > + default m > + depends on m > + help > + This builds bpfilter kernel module with embedded user mode helper > +endif > + > diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile > new file mode 100644 > index 000000000000..897eedae523e > --- /dev/null > +++ b/net/bpfilter/Makefile > @@ -0,0 +1,24 @@ > +# SPDX-License-Identifier: GPL-2.0 > +# > +# Makefile for the Linux BPFILTER layer. > +# > + > +hostprogs-y := bpfilter_umh > +bpfilter_umh-objs := main.o > +HOSTCFLAGS += -I. -Itools/include/ > + > +# a bit of elf magic to convert bpfilter_umh binary into a binary blob > +# inside bpfilter_umh.o elf file referenced by > +# _binary_net_bpfilter_bpfilter_umh_start symbol > +# which bpfilter_kern.c passes further into umh blob loader at run-time > +quiet_cmd_copy_umh = GEN $@ > + cmd_copy_umh = echo ':' > $(obj)/.bpfilter_umh.o.cmd; \ > + $(OBJCOPY) -I binary -O $(CONFIG_OUTPUT_FORMAT) \ > + -B `$(OBJDUMP) -f $<|grep architecture|cut -d, -f1|cut -d' ' -f2` \ > + --rename-section .data=.init.rodata $< $@ > + > +$(obj)/bpfilter_umh.o: $(obj)/bpfilter_umh > + $(call cmd,copy_umh) > + > +obj-$(CONFIG_BPFILTER_UMH) += bpfilter.o > +bpfilter-objs += bpfilter_kern.o bpfilter_umh.o > diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c > new file mode 100644 > index 000000000000..e0a6fdd5842b > --- /dev/null > +++ b/net/bpfilter/bpfilter_kern.c > @@ -0,0 +1,93 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include "msgfmt.h" > + > +#define UMH_start _binary_net_bpfilter_bpfilter_umh_start > +#define UMH_end _binary_net_bpfilter_bpfilter_umh_end > + > +extern char UMH_start; > +extern char UMH_end; > + > +static struct umh_info info; > + > +static void shutdown_umh(struct umh_info *info) > +{ > + struct task_struct *tsk; > + > + tsk = pid_task(find_vpid(info->pid), PIDTYPE_PID); > + if (tsk) > + force_sig(SIGKILL, tsk); > + fput(info->pipe_to_umh); > + fput(info->pipe_from_umh); > +} > + > +static void stop_umh(void) > +{ > + if (bpfilter_process_sockopt) { I worry about locking here.  Is it possible for two calls to  bpfilter_process_sockopt() to run in parallel, both fail, and thus both  call stop_umh()?  And if both end up calling shutdown_umh(), we double  fput(). > + bpfilter_process_sockopt = NULL; > + shutdown_umh(&info); > + } > +} > + > +static int __bpfilter_process_sockopt(struct sock *sk, int optname, > + char __user *optval, > + unsigned int optlen, bool is_set) > +{ > + struct mbox_request req; > + struct mbox_reply reply; > + loff_t pos; > + ssize_t n; > + > + req.is_set = is_set; > + req.pid = current->pid; > + req.cmd = optname; > + req.addr = (long)optval; > + req.len = optlen; > + n = __kernel_write(info.pipe_to_umh, &req, sizeof(req), &pos); > + if (n != sizeof(req)) { > + pr_err("write fail %zd\n", n); > + stop_umh(); > + return -EFAULT; > + } > + pos = 0; > + n = kernel_read(info.pipe_from_umh, &reply, sizeof(reply), &pos); > + if (n != sizeof(reply)) { > + pr_err("read fail %zd\n", n); > + stop_umh(); > + return -EFAULT; > + } > + return reply.status; > +} > + > +static int __init load_umh(void) > +{ > + int err; > + > + err = fork_usermode_blob(&UMH_start, &UMH_end - &UMH_start, &info); > + if (err) > + return err; > + pr_info("Loaded umh pid %d\n", info.pid); > + bpfilter_process_sockopt = &__bpfilter_process_sockopt; > + > + if (__bpfilter_process_sockopt(NULL, 0, 0, 0, 0) != 0) { > + stop_umh(); > + return -EFAULT; > + } > + return 0; > +} > + > +static void __exit fini_umh(void) > +{ > + stop_umh(); > +} > +module_init(load_umh); > +module_exit(fini_umh); > +MODULE_LICENSE("GPL"); > diff --git a/net/bpfilter/main.c b/net/bpfilter/main.c > new file mode 100644 > index 000000000000..81bbc1684896 > --- /dev/null > +++ b/net/bpfilter/main.c > @@ -0,0 +1,63 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#define _GNU_SOURCE > +#include > +#include > +#include > +#include > +#include > +#include > +#include "include/uapi/linux/bpf.h" > +#include > +#include "msgfmt.h" > + > +int debug_fd; > + > +static int handle_get_cmd(struct mbox_request *cmd) > +{ > + switch (cmd->cmd) { > + case 0: > + return 0; > + default: > + break; > + } > + return -ENOPROTOOPT; > +} > + > +static int handle_set_cmd(struct mbox_request *cmd) > +{ > + return -ENOPROTOOPT; > +} > + > +static void loop(void) > +{ > + while (1) { > + struct mbox_request req; > + struct mbox_reply reply; > + int n; > + > + n = read(0, &req, sizeof(req)); > + if (n != sizeof(req)) { > + dprintf(debug_fd, "invalid request %d\n", n); > + return; > + } > + > + reply.status = req.is_set ? > + handle_set_cmd(&req) : > + handle_get_cmd(&req); > + > + n = write(1, &reply, sizeof(reply)); > + if (n != sizeof(reply)) { > + dprintf(debug_fd, "reply failed %d\n", n); > + return; > + } > + } > +} > + > +int main(void) > +{ > + debug_fd = open("/dev/console", 00000002 | 00000100); Should probably handle failure of this open() call. > + dprintf(debug_fd, "Started bpfilter\n"); > + loop(); > + close(debug_fd); > + return 0; > +} > diff --git a/net/bpfilter/msgfmt.h b/net/bpfilter/msgfmt.h > new file mode 100644 > index 000000000000..94b9ac9e5114 > --- /dev/null > +++ b/net/bpfilter/msgfmt.h > @@ -0,0 +1,17 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _NET_BPFILTER_MSGFMT_H > +#define _NET_BPFTILER_MSGFMT_H Another bpftiler here, should be +#define _NET_BPFILTER_MSGFMT_H -Ed > + > +struct mbox_request { > + __u64 addr; > + __u32 len; > + __u32 is_set; > + __u32 cmd; > + __u32 pid; > +}; > + > +struct mbox_reply { > + __u32 status; > +}; > + > +#endif > diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile > index b379520f9133..7018f91c5a39 100644 > --- a/net/ipv4/Makefile > +++ b/net/ipv4/Makefile > @@ -16,6 +16,8 @@ obj-y := route.o inetpeer.o protocol.o \ > inet_fragment.o ping.o ip_tunnel_core.o gre_offload.o \ > metrics.o > > +obj-$(CONFIG_BPFILTER) += bpfilter/ > + > obj-$(CONFIG_NET_IP_TUNNEL) += ip_tunnel.o > obj-$(CONFIG_SYSCTL) += sysctl_net_ipv4.o > obj-$(CONFIG_PROC_FS) += proc.o > diff --git a/net/ipv4/bpfilter/Makefile b/net/ipv4/bpfilter/Makefile > new file mode 100644 > index 000000000000..ce262d76cc48 > --- /dev/null > +++ b/net/ipv4/bpfilter/Makefile > @@ -0,0 +1,2 @@ > +obj-$(CONFIG_BPFILTER) += sockopt.o > + > diff --git a/net/ipv4/bpfilter/sockopt.c b/net/ipv4/bpfilter/sockopt.c > new file mode 100644 > index 000000000000..42a96d2d8d05 > --- /dev/null > +++ b/net/ipv4/bpfilter/sockopt.c > @@ -0,0 +1,42 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#include > +#include > +#include > +#include > +#include > + > +int (*bpfilter_process_sockopt)(struct sock *sk, int optname, > + char __user *optval, > + unsigned int optlen, bool is_set); > +EXPORT_SYMBOL_GPL(bpfilter_process_sockopt); > + > +int bpfilter_mbox_request(struct sock *sk, int optname, char __user *optval, > + unsigned int optlen, bool is_set) > +{ > + if (!bpfilter_process_sockopt) { > + int err = request_module("bpfilter"); > + > + if (err) > + return err; > + if (!bpfilter_process_sockopt) > + return -ECHILD; > + } > + return bpfilter_process_sockopt(sk, optname, optval, optlen, is_set); > +} > + > +int bpfilter_ip_set_sockopt(struct sock *sk, int optname, char __user *optval, > + unsigned int optlen) > +{ > + return bpfilter_mbox_request(sk, optname, optval, optlen, true); > +} > + > +int bpfilter_ip_get_sockopt(struct sock *sk, int optname, char __user *optval, > + int __user *optlen) > +{ > + int len; > + > + if (get_user(len, optlen)) > + return -EFAULT; > + > + return bpfilter_mbox_request(sk, optname, optval, len, false); > +} > diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c > index 5ad2d8ed3a3f..e0791faacb24 100644 > --- a/net/ipv4/ip_sockglue.c > +++ b/net/ipv4/ip_sockglue.c > @@ -47,6 +47,8 @@ > #include > #include > > +#include > + > /* > * SOL_IP control messages. > */ > @@ -1244,6 +1246,11 @@ int ip_setsockopt(struct sock *sk, int level, > return -ENOPROTOOPT; > > err = do_ip_setsockopt(sk, level, optname, optval, optlen); > +#ifdef CONFIG_BPFILTER > + if (optname >= BPFILTER_IPT_SO_SET_REPLACE && > + optname < BPFILTER_IPT_SET_MAX) > + err = bpfilter_ip_set_sockopt(sk, optname, optval, optlen); > +#endif > #ifdef CONFIG_NETFILTER > /* we need to exclude all possible ENOPROTOOPTs except default case */ > if (err == -ENOPROTOOPT && optname != IP_HDRINCL && > @@ -1552,6 +1559,11 @@ int ip_getsockopt(struct sock *sk, int level, > int err; > > err = do_ip_getsockopt(sk, level, optname, optval, optlen, 0); > +#ifdef CONFIG_BPFILTER > + if (optname >= BPFILTER_IPT_SO_GET_INFO && > + optname < BPFILTER_IPT_GET_MAX) > + err = bpfilter_ip_get_sockopt(sk, optname, optval, optlen); > +#endif > #ifdef CONFIG_NETFILTER > /* we need to exclude all possible ENOPROTOOPTs except default case */ > if (err == -ENOPROTOOPT && optname != IP_PKTOPTIONS && > @@ -1584,6 +1596,11 @@ int compat_ip_getsockopt(struct sock *sk, int level, int optname, > err = do_ip_getsockopt(sk, level, optname, optval, optlen, > MSG_CMSG_COMPAT); > > +#ifdef CONFIG_BPFILTER > + if (optname >= BPFILTER_IPT_SO_GET_INFO && > + optname < BPFILTER_IPT_GET_MAX) > + err = bpfilter_ip_get_sockopt(sk, optname, optval, optlen); > +#endif > #ifdef CONFIG_NETFILTER > /* we need to exclude all possible ENOPROTOOPTs except default case */ > if (err == -ENOPROTOOPT && optname != IP_PKTOPTIONS &&