Date:   Thu, 20 May 2021 04:26:28 +0000
From:   Song Liu <songliubraving@...com>
To:     Dmitrii Banshchikov <me@...que.spb.ru>
CC:     "open list:BPF (Safe dynamic programs and tools)" 
        <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        "Andrii Nakryiko" <andrii@...nel.org>, Martin Lau <kafai@...com>,
        Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <netdev@...r.kernel.org>, Andrey Ignatov <rdna@...com>
Subject: Re: [PATCH bpf-next 06/11] bpfilter: Add struct match



> On May 17, 2021, at 3:53 PM, Dmitrii Banshchikov <me@...que.spb.ru> wrote:
> 
> struct match_ops defines polymorphic interface for matches. A match
> consists of pointers to struct match_ops and struct xt_entry_match which
> contains a payload for the match's type.
> 
> All match_ops are kept in map match_ops_map by their name.
> 
> Signed-off-by: Dmitrii Banshchikov <me@...que.spb.ru>
> 
[...]

> diff --git a/net/bpfilter/match-ops-map.h b/net/bpfilter/match-ops-map.h
> new file mode 100644
> index 000000000000..0ff57f2d8da8
> --- /dev/null
> +++ b/net/bpfilter/match-ops-map.h
> @@ -0,0 +1,48 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) 2021 Telegram FZ-LLC
> + */
> +
> +#ifndef NET_BPFILTER_MATCH_OPS_MAP_H
> +#define NET_BPFILTER_MATCH_OPS_MAP_H
> +
> +#include "map-common.h"
> +
> +#include <linux/err.h>
> +
> +#include <errno.h>
> +#include <string.h>
> +
> +#include "match.h"
> +
> +struct match_ops_map {
> +	struct hsearch_data index;
> +};

Do we plan to extend match_ops_map? Otherwise, we can just use 
hsearch_data in struct context. 

> +
> +static inline int create_match_ops_map(struct match_ops_map *map, size_t nelem)
> +{
> +	return create_map(&map->index, nelem);
> +}
> +
> +static inline const struct match_ops *match_ops_map_find(struct match_ops_map *map,
> +							 const char *name)
> +{
> +	const size_t namelen = strnlen(name, BPFILTER_EXTENSION_MAXNAMELEN);
> +
> +	if (namelen < BPFILTER_EXTENSION_MAXNAMELEN)
> +		return map_find(&map->index, name);
> +
> +	return ERR_PTR(-EINVAL);
> +}
> +
> +static inline int match_ops_map_insert(struct match_ops_map *map, const struct match_ops *match_ops)
> +{
> +	return map_insert(&map->index, match_ops->name, (void *)match_ops);
> +}
> +
> +static inline void free_match_ops_map(struct match_ops_map *map)
> +{
> +	free_map(&map->index);
> +}
> +
> +#endif // NET_BPFILTER_MATCT_OPS_MAP_H
> diff --git a/net/bpfilter/match.c b/net/bpfilter/match.c
> new file mode 100644
> index 000000000000..aeca1b93cd2d
> --- /dev/null
> +++ b/net/bpfilter/match.c
> @@ -0,0 +1,73 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2021 Telegram FZ-LLC
> + */
> +
> +#define _GNU_SOURCE
> +
> +#include "match.h"
> +
> +#include <linux/err.h>
> +#include <linux/netfilter/xt_tcpudp.h>

Besides xt_ filters, do we plan to support others? If so, we probably 
want separate files for each of them. 

> +
> +#include <errno.h>
> +#include <string.h>
> +
> +#include "bflog.h"
> +#include "context.h"
> +#include "match-ops-map.h"
> +
> +#define BPFILTER_ALIGN(__X) __ALIGN_KERNEL(__X, __alignof__(__u64))
> +#define MATCH_SIZE(type) (sizeof(struct bpfilter_ipt_match) + BPFILTER_ALIGN(sizeof(type)))
> +
> +static int udp_match_check(struct context *ctx, const struct bpfilter_ipt_match *ipt_match)
> +{
> +	const struct xt_udp *udp;
> +
> +	udp = (const struct xt_udp *)&ipt_match->data;
> +
> +	if (udp->invflags & XT_UDP_INV_MASK) {
> +		BFLOG_DEBUG(ctx, "cannot check match 'udp': invalid flags\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +const struct match_ops udp_match_ops = { .name = "udp",

And maybe we should name this one "xt_udp"? 

> +					 .size = MATCH_SIZE(struct xt_udp),
> +					 .revision = 0,
> +					 .check = udp_match_check };
> +
> +int init_match(struct context *ctx, const struct bpfilter_ipt_match *ipt_match, struct match *match)
> +{
> +	const size_t maxlen = sizeof(ipt_match->u.user.name);
> +	const struct match_ops *found;
> +	int err;
> +
> +	if (strnlen(ipt_match->u.user.name, maxlen) == maxlen) {
> +		BFLOG_DEBUG(ctx, "cannot init match: too long match name\n");
> +		return -EINVAL;
> +	}
> +
> +	found = match_ops_map_find(&ctx->match_ops_map, ipt_match->u.user.name);
> +	if (IS_ERR(found)) {
> +		BFLOG_DEBUG(ctx, "cannot find match by name: '%s'\n", ipt_match->u.user.name);
> +		return PTR_ERR(found);
> +	}
> +
> +	if (found->size != ipt_match->u.match_size ||
> +	    found->revision != ipt_match->u.user.revision) {
> +		BFLOG_DEBUG(ctx, "invalid match: '%s'\n", ipt_match->u.user.name);
> +		return -EINVAL;
> +	}
> +
> +	err = found->check(ctx, ipt_match);
> +	if (err)
> +		return err;
> +
> +	match->match_ops = found;
> +	match->ipt_match = ipt_match;
> +
> +	return 0;
> +}
> diff --git a/net/bpfilter/match.h b/net/bpfilter/match.h
> new file mode 100644
> index 000000000000..79b7c87016d4
> --- /dev/null
> +++ b/net/bpfilter/match.h
> @@ -0,0 +1,34 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) 2021 Telegram FZ-LLC
> + */
> +
> +#ifndef NET_BPFILTER_MATCH_H
> +#define NET_BPFILTER_MATCH_H
> +
> +#include "../../include/uapi/linux/bpfilter.h"
> +
> +#include <stdint.h>
> +
> +struct bpfilter_ipt_match;
> +struct context;
> +struct match_ops_map;
> +
> +struct match_ops {
> +	char name[BPFILTER_EXTENSION_MAXNAMELEN];

BPFILTER_EXTENSION_MAXNAMELEN is 29, so "size" below is mis-aligned. I guess
we can swap size and revision. 

> +	uint16_t size;
> +	uint8_t revision;
> +	int (*check)(struct context *ctx, const struct bpfilter_ipt_match *ipt_match);
> +};
> +
> +extern const struct match_ops udp_match_ops;
> +
> +struct match {
> +	const struct match_ops *match_ops;
> +	const struct bpfilter_ipt_match *ipt_match;
> +};

[...]

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