bpfilter: remove bpfilter

bpfilter was supposed to convert iptables filtering rules into
BPF programs on the fly, from the kernel, through a usermode
helper. The base code for the UMH was introduced in 2018, and
couple of attempts (2, 3) tried to introduce the BPF program
generate features but were abandoned.

bpfilter now sits in a kernel tree unused and unusable, occasionally
causing confusion amongst Linux users (4, 5).

As bpfilter is now developed in a dedicated repository on GitHub (6),
it was suggested a couple of times this year (LSFMM/BPF 2023,
LPC 2023) to remove the deprecated kernel part of the project. This
is the purpose of this patch.

[1]: https://lore.kernel.org/lkml/20180522022230.2492505-1-ast@kernel.org/
[2]: https://lore.kernel.org/bpf/20210829183608.2297877-1-me@ubique.spb.ru/#t
[3]: https://lore.kernel.org/lkml/20221224000402.476079-1-qde@naccy.de/
[4]: https://dxuuu.xyz/bpfilter.html
[5]: https://github.com/linuxkit/linuxkit/pull/3904
[6]: https://github.com/facebook/bpfilter

Signed-off-by: Quentin Deslandes <qde@naccy.de>
Link: https://lore.kernel.org/r/20231226130745.465988-1-qde@naccy.de
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 0 insertions, 136 deletions

diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
deleted file mode 100644
index 97e129e3f31c..000000000000
--- a/net/bpfilter/bpfilter_kern.c
+++ /dev/null
@@ -1,136 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-#include <linux/init.h>
-#include <linux/module.h>
-#include <linux/umh.h>
-#include <linux/bpfilter.h>
-#include <linux/sched.h>
-#include <linux/sched/signal.h>
-#include <linux/fs.h>
-#include <linux/file.h>
-#include "msgfmt.h"
-
-extern char bpfilter_umh_start;
-extern char bpfilter_umh_end;
-
-static void shutdown_umh(void)
-{
-	struct umd_info *info = &bpfilter_ops.info;
-	struct pid *tgid = info->tgid;
-
-	if (tgid) {
-		kill_pid(tgid, SIGKILL, 1);
-		wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
-		umd_cleanup_helper(info);
-	}
-}
-
-static void __stop_umh(void)
-{
-	if (IS_ENABLED(CONFIG_INET))
-		shutdown_umh();
-}
-
-static int bpfilter_send_req(struct mbox_request *req)
-{
-	struct mbox_reply reply;
-	loff_t pos = 0;
-	ssize_t n;
-
-	if (!bpfilter_ops.info.tgid)
-		return -EFAULT;
-	pos = 0;
-	n = kernel_write(bpfilter_ops.info.pipe_to_umh, req, sizeof(*req),
-			   &pos);
-	if (n != sizeof(*req)) {
-		pr_err("write fail %zd\n", n);
-		goto stop;
-	}
-	pos = 0;
-	n = kernel_read(bpfilter_ops.info.pipe_from_umh, &reply, sizeof(reply),
-			&pos);
-	if (n != sizeof(reply)) {
-		pr_err("read fail %zd\n", n);
-		goto stop;
-	}
-	return reply.status;
-stop:
-	__stop_umh();
-	return -EFAULT;
-}
-
-static int bpfilter_process_sockopt(struct sock *sk, int optname,
-				    sockptr_t optval, unsigned int optlen,
-				    bool is_set)
-{
-	struct mbox_request req = {
-		.is_set		= is_set,
-		.pid		= current->pid,
-		.cmd		= optname,
-		.addr		= (uintptr_t)optval.user,
-		.len		= optlen,
-	};
-	if (sockptr_is_kernel(optval)) {
-		pr_err("kernel access not supported\n");
-		return -EFAULT;
-	}
-	return bpfilter_send_req(&req);
-}
-
-static int start_umh(void)
-{
-	struct mbox_request req = { .pid = current->pid };
-	int err;
-
-	/* fork usermode process */
-	err = fork_usermode_driver(&bpfilter_ops.info);
-	if (err)
-		return err;
-	pr_info("Loaded bpfilter_umh pid %d\n", pid_nr(bpfilter_ops.info.tgid));
-
-	/* health check that usermode process started correctly */
-	if (bpfilter_send_req(&req) != 0) {
-		shutdown_umh();
-		return -EFAULT;
-	}
-
-	return 0;
-}
-
-static int __init load_umh(void)
-{
-	int err;
-
-	err = umd_load_blob(&bpfilter_ops.info,
-			    &bpfilter_umh_start,
-			    &bpfilter_umh_end - &bpfilter_umh_start);
-	if (err)
-		return err;
-
-	mutex_lock(&bpfilter_ops.lock);
-	err = start_umh();
-	if (!err && IS_ENABLED(CONFIG_INET)) {
-		bpfilter_ops.sockopt = &bpfilter_process_sockopt;
-		bpfilter_ops.start = &start_umh;
-	}
-	mutex_unlock(&bpfilter_ops.lock);
-	if (err)
-		umd_unload_blob(&bpfilter_ops.info);
-	return err;
-}
-
-static void __exit fini_umh(void)
-{
-	mutex_lock(&bpfilter_ops.lock);
-	if (IS_ENABLED(CONFIG_INET)) {
-		shutdown_umh();
-		bpfilter_ops.start = NULL;
-		bpfilter_ops.sockopt = NULL;
-	}
-	mutex_unlock(&bpfilter_ops.lock);
-
-	umd_unload_blob(&bpfilter_ops.info);
-}
-module_init(load_umh);
-module_exit(fini_umh);
-MODULE_LICENSE("GPL");