Bump?
On Wed, Dec 21, 2022 at 03:22:21PM +0100, Phil Sutter wrote:
> Allow for user space to provide an improved variant of the rule for
> actual use. The variant in NFTA_RULE_EXPRESSIONS may provide maximum
> compatibility for old user space tools (e.g. in outdated containers).
>
> The new attribute is also dumped back to user space, e.g. for comparison
> against the compatible variant.
>
> While being at it, improve nft_rule_policy for NFTA_RULE_EXPRESSIONS.
>
> Signed-off-by: Phil Sutter <phil@xxxxxx>
> ---
> Changes since v1:
> - Rename the new attribute as suggested
> - Avoid the changing attribute meaning - ACTUAL_EXPR will always contain
> the new variant, both on input and output
> - Rename the new struct nft_rule field accordingly
> - Add the new attribute to nft_rule_policy
> ---
> include/net/netfilter/nf_tables.h | 13 ++++++++
> include/uapi/linux/netfilter/nf_tables.h | 3 ++
> net/netfilter/nf_tables_api.c | 38 ++++++++++++++++++++----
> 3 files changed, 49 insertions(+), 5 deletions(-)
>
> diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
> index e69ce23566eab..e8446abb7620c 100644
> --- a/include/net/netfilter/nf_tables.h
> +++ b/include/net/netfilter/nf_tables.h
> @@ -946,10 +946,22 @@ struct nft_expr_ops {
> void *data;
> };
>
> +/**
> + * struct nft_dump_expr - compat expression blob for rule dumps
> + *
> + * @dlen: length of @data
> + * @data: blob used as payload of NFTA_RULE_EXPRESSIONS attribute
> + */
> +struct nft_dump_expr {
> + int dlen;
> + char data[];
> +};
> +
> /**
> * struct nft_rule - nf_tables rule
> *
> * @list: used internally
> + * @dump_expr: Expression blob to dump instead of live data
> * @handle: rule handle
> * @genmask: generation mask
> * @dlen: length of expression data
> @@ -958,6 +970,7 @@ struct nft_expr_ops {
> */
> struct nft_rule {
> struct list_head list;
> + struct nft_dump_expr *dump_expr;
> u64 handle:42,
> genmask:2,
> dlen:12,
> diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
> index cfa844da1ce61..3e0fc9e8784cb 100644
> --- a/include/uapi/linux/netfilter/nf_tables.h
> +++ b/include/uapi/linux/netfilter/nf_tables.h
> @@ -247,6 +247,8 @@ enum nft_chain_attributes {
> * @NFTA_RULE_USERDATA: user data (NLA_BINARY, NFT_USERDATA_MAXLEN)
> * @NFTA_RULE_ID: uniquely identifies a rule in a transaction (NLA_U32)
> * @NFTA_RULE_POSITION_ID: transaction unique identifier of the previous rule (NLA_U32)
> + * @NFTA_RULE_CHAIN_ID: add the rule to chain by ID, alternative to @NFTA_RULE_CHAIN (NLA_U32)
> + * @NFTA_RULE_ACTUAL_EXPR: list of expressions to really use if @NFTA_RULE_EXPRESSIONS must contain a compatible representation of the rule (NLA_NESTED: nft_expr_attributes)
> */
> enum nft_rule_attributes {
> NFTA_RULE_UNSPEC,
> @@ -261,6 +263,7 @@ enum nft_rule_attributes {
> NFTA_RULE_ID,
> NFTA_RULE_POSITION_ID,
> NFTA_RULE_CHAIN_ID,
> + NFTA_RULE_ACTUAL_EXPR,
> __NFTA_RULE_MAX
> };
> #define NFTA_RULE_MAX (__NFTA_RULE_MAX - 1)
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index 6269b0d9977c6..b3a14819f91f8 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -3019,7 +3019,7 @@ static const struct nla_policy nft_rule_policy[NFTA_RULE_MAX + 1] = {
> [NFTA_RULE_CHAIN] = { .type = NLA_STRING,
> .len = NFT_CHAIN_MAXNAMELEN - 1 },
> [NFTA_RULE_HANDLE] = { .type = NLA_U64 },
> - [NFTA_RULE_EXPRESSIONS] = { .type = NLA_NESTED },
> + [NFTA_RULE_EXPRESSIONS] = NLA_POLICY_NESTED_ARRAY(nft_expr_policy),
> [NFTA_RULE_COMPAT] = { .type = NLA_NESTED },
> [NFTA_RULE_POSITION] = { .type = NLA_U64 },
> [NFTA_RULE_USERDATA] = { .type = NLA_BINARY,
> @@ -3027,6 +3027,7 @@ static const struct nla_policy nft_rule_policy[NFTA_RULE_MAX + 1] = {
> [NFTA_RULE_ID] = { .type = NLA_U32 },
> [NFTA_RULE_POSITION_ID] = { .type = NLA_U32 },
> [NFTA_RULE_CHAIN_ID] = { .type = NLA_U32 },
> + [NFTA_RULE_ACTUAL_EXPR] = NLA_POLICY_NESTED_ARRAY(nft_expr_policy),
> };
>
> static int nf_tables_fill_rule_info(struct sk_buff *skb, struct net *net,
> @@ -3064,9 +3065,18 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, struct net *net,
> if (chain->flags & NFT_CHAIN_HW_OFFLOAD)
> nft_flow_rule_stats(chain, rule);
>
> - list = nla_nest_start_noflag(skb, NFTA_RULE_EXPRESSIONS);
> - if (list == NULL)
> + if (rule->dump_expr) {
> + if (nla_put(skb, NFTA_RULE_EXPRESSIONS,
> + rule->dump_expr->dlen, rule->dump_expr->data) < 0)
> + goto nla_put_failure;
> +
> + list = nla_nest_start_noflag(skb, NFTA_RULE_ACTUAL_EXPR);
> + } else {
> + list = nla_nest_start_noflag(skb, NFTA_RULE_EXPRESSIONS);
> + }
> + if (!list)
> goto nla_put_failure;
> +
> nft_rule_for_each_expr(expr, next, rule) {
> if (nft_expr_dump(skb, NFTA_LIST_ELEM, expr, reset) < 0)
> goto nla_put_failure;
> @@ -3366,6 +3376,7 @@ static void nf_tables_rule_destroy(const struct nft_ctx *ctx,
> nf_tables_expr_destroy(ctx, expr);
> expr = next;
> }
> + kfree(rule->dump_expr);
> kfree(rule);
> }
>
> @@ -3443,7 +3454,9 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
> struct nft_rule *rule, *old_rule = NULL;
> struct nft_expr_info *expr_info = NULL;
> u8 family = info->nfmsg->nfgen_family;
> + struct nft_dump_expr *dump_expr = NULL;
> struct nft_flow_rule *flow = NULL;
> + const struct nlattr *expr_nla;
> struct net *net = info->net;
> struct nft_userdata *udata;
> struct nft_table *table;
> @@ -3529,14 +3542,15 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
>
> n = 0;
> size = 0;
> - if (nla[NFTA_RULE_EXPRESSIONS]) {
> + expr_nla = nla[NFTA_RULE_ACTUAL_EXPR] ?: nla[NFTA_RULE_EXPRESSIONS];
> + if (expr_nla) {
> expr_info = kvmalloc_array(NFT_RULE_MAXEXPRS,
> sizeof(struct nft_expr_info),
> GFP_KERNEL);
> if (!expr_info)
> return -ENOMEM;
>
> - nla_for_each_nested(tmp, nla[NFTA_RULE_EXPRESSIONS], rem) {
> + nla_for_each_nested(tmp, expr_nla, rem) {
> err = -EINVAL;
> if (nla_type(tmp) != NFTA_LIST_ELEM)
> goto err_release_expr;
> @@ -3556,6 +3570,19 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
> if (size >= 1 << 12)
> goto err_release_expr;
>
> + if (nla[NFTA_RULE_ACTUAL_EXPR]) {
> + int dlen = nla_len(nla[NFTA_RULE_EXPRESSIONS]);
> +
> + /* store unused NFTA_RULE_EXPRESSIONS for later */
> + dump_expr = kvmalloc(sizeof(*dump_expr) + dlen, GFP_KERNEL);
> + if (!dump_expr) {
> + err = -ENOMEM;
> + goto err_release_expr;
> + }
> + dump_expr->dlen = dlen;
> + nla_memcpy(dump_expr->data, nla[NFTA_RULE_EXPRESSIONS], dlen);
> + }
> +
> if (nla[NFTA_RULE_USERDATA]) {
> ulen = nla_len(nla[NFTA_RULE_USERDATA]);
> if (ulen > 0)
> @@ -3572,6 +3599,7 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
> rule->handle = handle;
> rule->dlen = size;
> rule->udata = ulen ? 1 : 0;
> + rule->dump_expr = dump_expr;
>
> if (ulen) {
> udata = nft_userdata(rule);
> --
> 2.38.0
>
>
