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374d345d9b
We currently push everyone to use padding to align 64b values in netlink. Un-padded nla_put_u64() doesn't even exist any more. The story behind this possibly start with this thread: https://lore.kernel.org/netdev/20121204.130914.1457976839967676240.davem@davemloft.net/ where DaveM was concerned about the alignment of a structure containing 64b stats. If user space tries to access such struct directly: struct some_stats *stats = nla_data(attr); printf("A: %llu", stats->a); lack of alignment may become problematic for some architectures. These days we most often put every single member in a separate attribute, meaning that the code above would use a helper like nla_get_u64(), which can deal with alignment internally. Even for arches which don't have good unaligned access - access aligned to 4B should be pretty efficient. Kernel and well known libraries deal with unaligned input already. Padded 64b is quite space-inefficient (64b + pad means at worst 16B per attr vs 32b which takes 8B). It is also more typing: if (nla_put_u64_pad(rsp, NETDEV_A_SOMETHING_SOMETHING, value, NETDEV_A_SOMETHING_PAD)) Create a new attribute type which will use 32 bits at netlink level if value is small enough (probably most of the time?), and (4B-aligned) 64 bits otherwise. Kernel API is just: if (nla_put_uint(rsp, NETDEV_A_SOMETHING_SOMETHING, value)) Calling this new type "just" sint / uint with no specific size will hopefully also make people more comfortable with using it. Currently telling people "don't use u8, you may need the bits, and netlink will round up to 4B, anyway" is the #1 comment we give to newcomers. In terms of netlink layout it looks like this: 0 4 8 12 16 32b: [nlattr][ u32 ] 64b: [ pad ][nlattr][ u64 ] uint(32) [nlattr][ u32 ] uint(64) [nlattr][ u64 ] Signed-off-by: Jakub Kicinski <kuba@kernel.org> Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Signed-off-by: David S. Miller <davem@davemloft.net>
489 lines
12 KiB
C
489 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* NETLINK Policy advertisement to userspace
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*
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* Authors: Johannes Berg <johannes@sipsolutions.net>
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*
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* Copyright 2019 Intel Corporation
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*/
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/types.h>
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#include <net/netlink.h>
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#define INITIAL_POLICIES_ALLOC 10
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struct netlink_policy_dump_state {
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unsigned int policy_idx;
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unsigned int attr_idx;
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unsigned int n_alloc;
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struct {
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const struct nla_policy *policy;
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unsigned int maxtype;
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} policies[] __counted_by(n_alloc);
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};
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static int add_policy(struct netlink_policy_dump_state **statep,
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const struct nla_policy *policy,
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unsigned int maxtype)
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{
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struct netlink_policy_dump_state *state = *statep;
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unsigned int old_n_alloc, n_alloc, i;
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if (!policy || !maxtype)
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return 0;
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for (i = 0; i < state->n_alloc; i++) {
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if (state->policies[i].policy == policy &&
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state->policies[i].maxtype == maxtype)
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return 0;
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if (!state->policies[i].policy) {
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state->policies[i].policy = policy;
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state->policies[i].maxtype = maxtype;
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return 0;
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}
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}
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n_alloc = state->n_alloc + INITIAL_POLICIES_ALLOC;
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state = krealloc(state, struct_size(state, policies, n_alloc),
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GFP_KERNEL);
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if (!state)
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return -ENOMEM;
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old_n_alloc = state->n_alloc;
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state->n_alloc = n_alloc;
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memset(&state->policies[old_n_alloc], 0,
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flex_array_size(state, policies, n_alloc - old_n_alloc));
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state->policies[old_n_alloc].policy = policy;
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state->policies[old_n_alloc].maxtype = maxtype;
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*statep = state;
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return 0;
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}
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/**
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* netlink_policy_dump_get_policy_idx - retrieve policy index
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* @state: the policy dump state
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* @policy: the policy to find
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* @maxtype: the policy's maxattr
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*
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* Returns: the index of the given policy in the dump state
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*
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* Call this to find a policy index when you've added multiple and e.g.
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* need to tell userspace which command has which policy (by index).
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*
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* Note: this will WARN and return 0 if the policy isn't found, which
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* means it wasn't added in the first place, which would be an
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* internal consistency bug.
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*/
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int netlink_policy_dump_get_policy_idx(struct netlink_policy_dump_state *state,
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const struct nla_policy *policy,
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unsigned int maxtype)
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{
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unsigned int i;
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if (WARN_ON(!policy || !maxtype))
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return 0;
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for (i = 0; i < state->n_alloc; i++) {
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if (state->policies[i].policy == policy &&
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state->policies[i].maxtype == maxtype)
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return i;
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}
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WARN_ON(1);
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return 0;
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}
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static struct netlink_policy_dump_state *alloc_state(void)
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{
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struct netlink_policy_dump_state *state;
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state = kzalloc(struct_size(state, policies, INITIAL_POLICIES_ALLOC),
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GFP_KERNEL);
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if (!state)
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return ERR_PTR(-ENOMEM);
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state->n_alloc = INITIAL_POLICIES_ALLOC;
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return state;
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}
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/**
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* netlink_policy_dump_add_policy - add a policy to the dump
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* @pstate: state to add to, may be reallocated, must be %NULL the first time
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* @policy: the new policy to add to the dump
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* @maxtype: the new policy's max attr type
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*
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* Returns: 0 on success, a negative error code otherwise.
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*
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* Call this to allocate a policy dump state, and to add policies to it. This
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* should be called from the dump start() callback.
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*
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* Note: on failures, any previously allocated state is freed.
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*/
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int netlink_policy_dump_add_policy(struct netlink_policy_dump_state **pstate,
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const struct nla_policy *policy,
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unsigned int maxtype)
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{
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struct netlink_policy_dump_state *state = *pstate;
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unsigned int policy_idx;
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int err;
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if (!state) {
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state = alloc_state();
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if (IS_ERR(state))
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return PTR_ERR(state);
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}
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/*
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* walk the policies and nested ones first, and build
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* a linear list of them.
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*/
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err = add_policy(&state, policy, maxtype);
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if (err)
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goto err_try_undo;
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for (policy_idx = 0;
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policy_idx < state->n_alloc && state->policies[policy_idx].policy;
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policy_idx++) {
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const struct nla_policy *policy;
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unsigned int type;
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policy = state->policies[policy_idx].policy;
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for (type = 0;
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type <= state->policies[policy_idx].maxtype;
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type++) {
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switch (policy[type].type) {
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case NLA_NESTED:
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case NLA_NESTED_ARRAY:
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err = add_policy(&state,
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policy[type].nested_policy,
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policy[type].len);
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if (err)
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goto err_try_undo;
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break;
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default:
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break;
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}
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}
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}
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*pstate = state;
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return 0;
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err_try_undo:
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/* Try to preserve reasonable unwind semantics - if we're starting from
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* scratch clean up fully, otherwise record what we got and caller will.
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*/
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if (!*pstate)
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netlink_policy_dump_free(state);
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else
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*pstate = state;
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return err;
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}
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static bool
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netlink_policy_dump_finished(struct netlink_policy_dump_state *state)
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{
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return state->policy_idx >= state->n_alloc ||
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!state->policies[state->policy_idx].policy;
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}
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/**
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* netlink_policy_dump_loop - dumping loop indicator
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* @state: the policy dump state
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*
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* Returns: %true if the dump continues, %false otherwise
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*
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* Note: this frees the dump state when finishing
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*/
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bool netlink_policy_dump_loop(struct netlink_policy_dump_state *state)
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{
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return !netlink_policy_dump_finished(state);
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}
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int netlink_policy_dump_attr_size_estimate(const struct nla_policy *pt)
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{
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/* nested + type */
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int common = 2 * nla_attr_size(sizeof(u32));
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switch (pt->type) {
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case NLA_UNSPEC:
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case NLA_REJECT:
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/* these actually don't need any space */
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return 0;
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case NLA_NESTED:
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case NLA_NESTED_ARRAY:
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/* common, policy idx, policy maxattr */
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return common + 2 * nla_attr_size(sizeof(u32));
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case NLA_U8:
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case NLA_U16:
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case NLA_U32:
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case NLA_U64:
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case NLA_MSECS:
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case NLA_S8:
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case NLA_S16:
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case NLA_S32:
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case NLA_S64:
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case NLA_SINT:
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case NLA_UINT:
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/* maximum is common, u64 min/max with padding */
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return common +
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2 * (nla_attr_size(0) + nla_attr_size(sizeof(u64)));
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case NLA_BITFIELD32:
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return common + nla_attr_size(sizeof(u32));
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case NLA_STRING:
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case NLA_NUL_STRING:
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case NLA_BINARY:
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/* maximum is common, u32 min-length/max-length */
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return common + 2 * nla_attr_size(sizeof(u32));
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case NLA_FLAG:
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return common;
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}
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/* this should then cause a warning later */
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return 0;
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}
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static int
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__netlink_policy_dump_write_attr(struct netlink_policy_dump_state *state,
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struct sk_buff *skb,
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const struct nla_policy *pt,
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int nestattr)
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{
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int estimate = netlink_policy_dump_attr_size_estimate(pt);
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enum netlink_attribute_type type;
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struct nlattr *attr;
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attr = nla_nest_start(skb, nestattr);
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if (!attr)
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return -ENOBUFS;
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switch (pt->type) {
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default:
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case NLA_UNSPEC:
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case NLA_REJECT:
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/* skip - use NLA_MIN_LEN to advertise such */
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nla_nest_cancel(skb, attr);
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return -ENODATA;
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case NLA_NESTED:
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type = NL_ATTR_TYPE_NESTED;
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fallthrough;
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case NLA_NESTED_ARRAY:
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if (pt->type == NLA_NESTED_ARRAY)
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type = NL_ATTR_TYPE_NESTED_ARRAY;
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if (state && pt->nested_policy && pt->len &&
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(nla_put_u32(skb, NL_POLICY_TYPE_ATTR_POLICY_IDX,
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netlink_policy_dump_get_policy_idx(state,
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pt->nested_policy,
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pt->len)) ||
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nla_put_u32(skb, NL_POLICY_TYPE_ATTR_POLICY_MAXTYPE,
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pt->len)))
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goto nla_put_failure;
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break;
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case NLA_U8:
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case NLA_U16:
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case NLA_U32:
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case NLA_U64:
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case NLA_UINT:
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case NLA_MSECS: {
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struct netlink_range_validation range;
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if (pt->type == NLA_U8)
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type = NL_ATTR_TYPE_U8;
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else if (pt->type == NLA_U16)
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type = NL_ATTR_TYPE_U16;
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else if (pt->type == NLA_U32)
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type = NL_ATTR_TYPE_U32;
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else if (pt->type == NLA_U64)
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type = NL_ATTR_TYPE_U64;
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else
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type = NL_ATTR_TYPE_UINT;
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if (pt->validation_type == NLA_VALIDATE_MASK) {
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if (nla_put_u64_64bit(skb, NL_POLICY_TYPE_ATTR_MASK,
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pt->mask,
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NL_POLICY_TYPE_ATTR_PAD))
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goto nla_put_failure;
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break;
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}
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nla_get_range_unsigned(pt, &range);
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if (nla_put_u64_64bit(skb, NL_POLICY_TYPE_ATTR_MIN_VALUE_U,
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range.min, NL_POLICY_TYPE_ATTR_PAD) ||
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nla_put_u64_64bit(skb, NL_POLICY_TYPE_ATTR_MAX_VALUE_U,
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range.max, NL_POLICY_TYPE_ATTR_PAD))
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goto nla_put_failure;
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break;
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}
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case NLA_S8:
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case NLA_S16:
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case NLA_S32:
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case NLA_S64:
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case NLA_SINT: {
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struct netlink_range_validation_signed range;
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if (pt->type == NLA_S8)
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type = NL_ATTR_TYPE_S8;
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else if (pt->type == NLA_S16)
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type = NL_ATTR_TYPE_S16;
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else if (pt->type == NLA_S32)
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type = NL_ATTR_TYPE_S32;
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else if (pt->type == NLA_S64)
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type = NL_ATTR_TYPE_S64;
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else
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type = NL_ATTR_TYPE_SINT;
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nla_get_range_signed(pt, &range);
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if (nla_put_s64(skb, NL_POLICY_TYPE_ATTR_MIN_VALUE_S,
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range.min, NL_POLICY_TYPE_ATTR_PAD) ||
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nla_put_s64(skb, NL_POLICY_TYPE_ATTR_MAX_VALUE_S,
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range.max, NL_POLICY_TYPE_ATTR_PAD))
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goto nla_put_failure;
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break;
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}
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case NLA_BITFIELD32:
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type = NL_ATTR_TYPE_BITFIELD32;
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if (nla_put_u32(skb, NL_POLICY_TYPE_ATTR_BITFIELD32_MASK,
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pt->bitfield32_valid))
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goto nla_put_failure;
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break;
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case NLA_STRING:
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case NLA_NUL_STRING:
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case NLA_BINARY:
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if (pt->type == NLA_STRING)
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type = NL_ATTR_TYPE_STRING;
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else if (pt->type == NLA_NUL_STRING)
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type = NL_ATTR_TYPE_NUL_STRING;
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else
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type = NL_ATTR_TYPE_BINARY;
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if (pt->validation_type == NLA_VALIDATE_RANGE ||
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pt->validation_type == NLA_VALIDATE_RANGE_WARN_TOO_LONG) {
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struct netlink_range_validation range;
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nla_get_range_unsigned(pt, &range);
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if (range.min &&
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nla_put_u32(skb, NL_POLICY_TYPE_ATTR_MIN_LENGTH,
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range.min))
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goto nla_put_failure;
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if (range.max < U16_MAX &&
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nla_put_u32(skb, NL_POLICY_TYPE_ATTR_MAX_LENGTH,
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range.max))
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goto nla_put_failure;
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} else if (pt->len &&
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nla_put_u32(skb, NL_POLICY_TYPE_ATTR_MAX_LENGTH,
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pt->len)) {
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goto nla_put_failure;
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}
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break;
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case NLA_FLAG:
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type = NL_ATTR_TYPE_FLAG;
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break;
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}
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if (nla_put_u32(skb, NL_POLICY_TYPE_ATTR_TYPE, type))
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goto nla_put_failure;
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nla_nest_end(skb, attr);
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WARN_ON(attr->nla_len > estimate);
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return 0;
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nla_put_failure:
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nla_nest_cancel(skb, attr);
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return -ENOBUFS;
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}
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/**
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* netlink_policy_dump_write_attr - write a given attribute policy
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* @skb: the message skb to write to
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* @pt: the attribute's policy
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* @nestattr: the nested attribute ID to use
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*
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* Returns: 0 on success, an error code otherwise; -%ENODATA is
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* special, indicating that there's no policy data and
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* the attribute is generally rejected.
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*/
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int netlink_policy_dump_write_attr(struct sk_buff *skb,
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const struct nla_policy *pt,
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int nestattr)
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{
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return __netlink_policy_dump_write_attr(NULL, skb, pt, nestattr);
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}
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/**
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* netlink_policy_dump_write - write current policy dump attributes
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* @skb: the message skb to write to
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* @state: the policy dump state
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*
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* Returns: 0 on success, an error code otherwise
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*/
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int netlink_policy_dump_write(struct sk_buff *skb,
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struct netlink_policy_dump_state *state)
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{
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const struct nla_policy *pt;
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struct nlattr *policy;
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bool again;
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int err;
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send_attribute:
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again = false;
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pt = &state->policies[state->policy_idx].policy[state->attr_idx];
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policy = nla_nest_start(skb, state->policy_idx);
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if (!policy)
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return -ENOBUFS;
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err = __netlink_policy_dump_write_attr(state, skb, pt, state->attr_idx);
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if (err == -ENODATA) {
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nla_nest_cancel(skb, policy);
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again = true;
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goto next;
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} else if (err) {
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goto nla_put_failure;
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}
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/* finish and move state to next attribute */
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nla_nest_end(skb, policy);
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next:
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state->attr_idx += 1;
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if (state->attr_idx > state->policies[state->policy_idx].maxtype) {
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state->attr_idx = 0;
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state->policy_idx++;
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}
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if (again) {
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if (netlink_policy_dump_finished(state))
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return -ENODATA;
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goto send_attribute;
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}
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return 0;
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nla_put_failure:
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nla_nest_cancel(skb, policy);
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return -ENOBUFS;
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}
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/**
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* netlink_policy_dump_free - free policy dump state
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* @state: the policy dump state to free
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*
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* Call this from the done() method to ensure dump state is freed.
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*/
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void netlink_policy_dump_free(struct netlink_policy_dump_state *state)
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{
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kfree(state);
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}
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