* [PATCH] bpf, docs: document BPF_MAP_TYPE_HASH and variants
@ 2022-07-13 21:16 Donald Hunter
2022-07-13 23:30 ` sdf
2022-07-14 1:12 ` Bagas Sanjaya
0 siblings, 2 replies; 7+ messages in thread
From: Donald Hunter @ 2022-07-13 21:16 UTC (permalink / raw)
To: bpf, linux-doc; +Cc: Jonathan Corbet, Donald Hunter
This commit adds documentation for BPF_MAP_TYPE_HASH including kernel
version introduced, usage and examples. It also documents
BPF_MAP_TYPE_PERCPU_HASH, BPF_MAP_TYPE_LRU_HASH and
BPF_MAP_TYPE_LRU_PERCPU_HASH which are similar.
Note that this file is included in the BPF documentation by the glob in
Documentation/bpf/maps.rst
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
---
Documentation/bpf/map_hash.rst | 176 +++++++++++++++++++++++++++++++++
1 file changed, 176 insertions(+)
create mode 100644 Documentation/bpf/map_hash.rst
diff --git a/Documentation/bpf/map_hash.rst b/Documentation/bpf/map_hash.rst
new file mode 100644
index 000000000000..991452e70cc9
--- /dev/null
+++ b/Documentation/bpf/map_hash.rst
@@ -0,0 +1,176 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+.. Copyright (C) 2021 Red Hat, Inc.
+
+===============================================
+BPF_MAP_TYPE_HASH, with PERCPU and LRU Variants
+===============================================
+
+.. note::
+ - ``BPF_MAP_TYPE_HASH`` was introduced in kernel version 3.19
+ - ``BPF_MAP_TYPE_PERCPU_HASH`` was introduced in version 4.6
+ - Both ``BPF_MAP_TYPE_LRU_HASH`` and ``BPF_MAP_TYPE_LRU_PERCPU_HASH``
+ were introduced in version 4.10
+
+``BPF_MAP_TYPE_HASH`` and ``BPF_MAP_TYPE_PERCPU_HASH`` provide general
+purpose hash map storage. Both the key and the value can be structs,
+allowing for composite keys and values. The maximum number of entries is
+defined in max_entries and is limited to 2^32. The kernel is responsible
+for allocating and freeing key/value pairs, up to the max_entries limit
+that you specify. ``BPF_MAP_TYPE_PERCPU_HASH`` provides a separate hash
+table per CPU.
+
+Values stored in ``BPF_MAP_TYPE_HASH`` can be accessed concurrently by
+programs running on different CPUs. Since Kernel version 5.1, the BPF
+infrastructure provides ``struct bpf_spin_lock`` to synchronize access.
+
+The ``BPF_MAP_TYPE_LRU_HASH`` and ``BPF_MAP_TYPE_LRU_PERCPU_HASH``
+variants add LRU semantics to their respective hash tables. An LRU hash
+will automatically evict the least recently used entries when the hash
+table reaches capacity. An LRU hash maintains an internal LRU list that
+is used to select elements for eviction. This internal LRU list is
+shared across CPUs but it is possible to request a per CPU LRU list with
+the ``BPF_F_NO_COMMON_LRU`` flag when calling ``bpf_map_create``.
+
+Usage
+=====
+
+.. c:function::
+ long bpf_map_update_elem(struct bpf_map *map, const void *key, const void *value, u60 flags)
+
+Hash entries can be added or updated using the ``bpf_map_update_elem()``
+helper. This helper replaces existing elements atomically. The ``flags``
+parameter can be used to control the update behaviour:
+
+- ``BPF_ANY`` will create a new element or update an existing element
+- ``BPF_NOTEXIST`` will create a new element only if one did not already
+ exist
+- ``BPF_EXIST`` will update an existing element
+
+``bpf_map_update_elem()`` returns 0 on success, or negative error in
+case of failure.
+
+.. c:function::
+ void *bpf_map_lookup_elem(struct bpf_map *map, const void *key)
+
+Hash entries can be retrieved using the ``bpf_map_lookup_elem()``
+helper. This helper returns a pointer to the value associated with
+``key``, or ``NULL`` if no entry was found.
+
+.. c:function::
+ long bpf_map_delete_elem(struct bpf_map *map, const void *key)
+
+Hash entries can be deleted using the ``bpf_map_delete_elem()``
+helper. This helper will return 0 on success, or negative error in case
+of failure.
+
+Per CPU Hashes
+--------------
+
+For ``BPF_MAP_TYPE_PERCPU_HASH`` and ``BPF_MAP_TYPE_LRU_PERCPU_HASH``
+the ``bpf_map_update_elem()`` and ``bpf_map_lookup_elem()`` helpers
+automatically access the hash slot for the current CPU.
+
+.. c:function::
+ void *bpf_map_lookup_percpu_elem(struct bpf_map *map, const void *key, u32 cpu)
+
+The ``bpf_map_lookup_percpu_elem()`` helper can be used to lookup the
+value in the hash slot for a specific CPU. Returns value associated with
+``key`` on ``cpu`` , or ``NULL`` if no entry was found or ``cpu`` is
+invalid.
+
+Userspace
+---------
+
+.. c:function::
+ int bpf_map_get_next_key (int fd, const void *cur_key, void *next_key)
+
+In userspace, is possible to iterate through the keys of a hash using
+the ``bpf_map_get_next_key()`` function. The first key can be fetched by
+calling ``bpf_map_get_next_key()`` with ``cur_key`` set to
+``NULL``. Subsequent calls will fetch the next key that follows the
+current key. ``bpf_map_get_next_key()`` returns 0 on success, -ENOENT if
+cur_key is the last key in the hash, or negative error in case of
+failure.
+
+Examples
+========
+
+Please see the ``tools/testing/selftests/bpf`` directory for functional
+examples. This sample code demonstrates API usage.
+
+Kernel
+------
+
+.. code-block:: c
+
+ #include <linux/bpf.h>
+ #include <bpf/bpf_helpers.h>
+
+ struct key {
+ __u32 srcip;
+ };
+
+ struct value {
+ __u64 packets;
+ __u64 bytes;
+ };
+
+ struct {
+ __uint(type, BPF_MAP_TYPE_LRU_HASH);
+ __uint(max_entries, 32);
+ __type(key, struct key);
+ __type(value, struct value);
+ } packet_stats SEC(".maps");
+
+ static inline void count_by_srcip(__u32 srcip, int bytes)
+ {
+ struct key key = {
+ .srcip = srcip
+ };
+ struct value *value = bpf_map_lookup_elem(&packet_stats, &key);
+ if (value) {
+ __sync_fetch_and_add(&value->packets, 1);
+ __sync_fetch_and_add(&value->bytes, bytes);
+ } else {
+ struct value newval = { 1, bytes };
+ bpf_map_update_elem(&packet_stats, &key, &newval, BPF_NOEXIST);
+ }
+ }
+
+Userspace
+---------
+
+.. code-block:: c
+
+ #include <bpf/libbpf.h>
+ #include <bpf/bpf.h>
+
+ static void print_values(int map_fd)
+ {
+ struct key *cur_key = NULL;
+ struct key next_key;
+ int next;
+ do {
+ next = bpf_map_get_next_key(stats_fd, cur_key, &next_key);
+ if (next == -ENOENT)
+ break;
+ if (next < 0) {
+ fprintf(stderr, "bpf_map_get_next_key %d returned %s\n", stats_fd, strerror(-next));
+ break;
+ }
+
+ struct in_addr src_addr = {
+ .s_addr = next_key.srcip
+ };
+ char *src_ip = inet_ntoa(src_addr);
+
+ struct value value;
+ int ret = bpf_map_lookup_elem(stats_fd, &next_key, &value);
+ if (ret < 0) {
+ fprintf(stderr, "Failed to lookup elem with key %s: %s\n", src_ip, strerror(-ret));
+ break;
+ }
+ printf("%s: %lld packets, %lld bytes\n", src_ip, value.packets, value.bytes);
+ cur_key = &next_key;
+ } while (next == 0);
+ }
--
2.35.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] bpf, docs: document BPF_MAP_TYPE_HASH and variants
2022-07-13 21:16 [PATCH] bpf, docs: document BPF_MAP_TYPE_HASH and variants Donald Hunter
@ 2022-07-13 23:30 ` sdf
2022-07-14 22:20 ` Donald Hunter
2022-07-14 1:12 ` Bagas Sanjaya
1 sibling, 1 reply; 7+ messages in thread
From: sdf @ 2022-07-13 23:30 UTC (permalink / raw)
To: Donald Hunter; +Cc: bpf, linux-doc, Jonathan Corbet
On 07/13, Donald Hunter wrote:
> This commit adds documentation for BPF_MAP_TYPE_HASH including kernel
> version introduced, usage and examples. It also documents
> BPF_MAP_TYPE_PERCPU_HASH, BPF_MAP_TYPE_LRU_HASH and
> BPF_MAP_TYPE_LRU_PERCPU_HASH which are similar.
> Note that this file is included in the BPF documentation by the glob in
> Documentation/bpf/maps.rst
> Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
> ---
> Documentation/bpf/map_hash.rst | 176 +++++++++++++++++++++++++++++++++
> 1 file changed, 176 insertions(+)
> create mode 100644 Documentation/bpf/map_hash.rst
> diff --git a/Documentation/bpf/map_hash.rst
> b/Documentation/bpf/map_hash.rst
> new file mode 100644
> index 000000000000..991452e70cc9
> --- /dev/null
> +++ b/Documentation/bpf/map_hash.rst
> @@ -0,0 +1,176 @@
> +.. SPDX-License-Identifier: GPL-2.0-only
> +.. Copyright (C) 2021 Red Hat, Inc.
> +
> +===============================================
> +BPF_MAP_TYPE_HASH, with PERCPU and LRU Variants
> +===============================================
> +
> +.. note::
> + - ``BPF_MAP_TYPE_HASH`` was introduced in kernel version 3.19
> + - ``BPF_MAP_TYPE_PERCPU_HASH`` was introduced in version 4.6
> + - Both ``BPF_MAP_TYPE_LRU_HASH`` and ``BPF_MAP_TYPE_LRU_PERCPU_HASH``
> + were introduced in version 4.10
> +
> +``BPF_MAP_TYPE_HASH`` and ``BPF_MAP_TYPE_PERCPU_HASH`` provide general
> +purpose hash map storage. Both the key and the value can be structs,
> +allowing for composite keys and values. The maximum number of entries is
> +defined in max_entries and is limited to 2^32. The kernel is responsible
Do we really need to mention 2^32 limit here? It really depends on
the key/value sizes, right?
Instead, might be worth talking about how/when this memory is allocated and
mention BPF_F_NO_PREALLOC?
> +for allocating and freeing key/value pairs, up to the max_entries limit
> +that you specify. ``BPF_MAP_TYPE_PERCPU_HASH`` provides a separate hash
> +table per CPU.
> +
> +Values stored in ``BPF_MAP_TYPE_HASH`` can be accessed concurrently by
> +programs running on different CPUs. Since Kernel version 5.1, the BPF
> +infrastructure provides ``struct bpf_spin_lock`` to synchronize access.
> +
> +The ``BPF_MAP_TYPE_LRU_HASH`` and ``BPF_MAP_TYPE_LRU_PERCPU_HASH``
> +variants add LRU semantics to their respective hash tables. An LRU hash
> +will automatically evict the least recently used entries when the hash
> +table reaches capacity. An LRU hash maintains an internal LRU list that
> +is used to select elements for eviction. This internal LRU list is
> +shared across CPUs but it is possible to request a per CPU LRU list with
> +the ``BPF_F_NO_COMMON_LRU`` flag when calling ``bpf_map_create``.
> +
> +Usage
> +=====
> +
> +.. c:function::
> + long bpf_map_update_elem(struct bpf_map *map, const void *key, const
> void *value, u60 flags)
s/u60/u64/
> +
> +Hash entries can be added or updated using the ``bpf_map_update_elem()``
> +helper. This helper replaces existing elements atomically. The ``flags``
> +parameter can be used to control the update behaviour:
> +
> +- ``BPF_ANY`` will create a new element or update an existing element
> +- ``BPF_NOTEXIST`` will create a new element only if one did not already
> + exist
> +- ``BPF_EXIST`` will update an existing element
> +
> +``bpf_map_update_elem()`` returns 0 on success, or negative error in
> +case of failure.
> +
> +.. c:function::
> + void *bpf_map_lookup_elem(struct bpf_map *map, const void *key)
> +
> +Hash entries can be retrieved using the ``bpf_map_lookup_elem()``
> +helper. This helper returns a pointer to the value associated with
> +``key``, or ``NULL`` if no entry was found.
> +
> +.. c:function::
> + long bpf_map_delete_elem(struct bpf_map *map, const void *key)
> +
> +Hash entries can be deleted using the ``bpf_map_delete_elem()``
> +helper. This helper will return 0 on success, or negative error in case
> +of failure.
> +
> +Per CPU Hashes
> +--------------
> +
> +For ``BPF_MAP_TYPE_PERCPU_HASH`` and ``BPF_MAP_TYPE_LRU_PERCPU_HASH``
> +the ``bpf_map_update_elem()`` and ``bpf_map_lookup_elem()`` helpers
> +automatically access the hash slot for the current CPU.
> +
> +.. c:function::
> + void *bpf_map_lookup_percpu_elem(struct bpf_map *map, const void
> *key, u32 cpu)
> +
> +The ``bpf_map_lookup_percpu_elem()`` helper can be used to lookup the
> +value in the hash slot for a specific CPU. Returns value associated with
> +``key`` on ``cpu`` , or ``NULL`` if no entry was found or ``cpu`` is
> +invalid.
> +
> +Userspace
> +---------
> +
> +.. c:function::
> + int bpf_map_get_next_key (int fd, const void *cur_key, void *next_key)
> +
> +In userspace, is possible to iterate through the keys of a hash using
> +the ``bpf_map_get_next_key()`` function. The first key can be fetched by
> +calling ``bpf_map_get_next_key()`` with ``cur_key`` set to
> +``NULL``. Subsequent calls will fetch the next key that follows the
> +current key. ``bpf_map_get_next_key()`` returns 0 on success, -ENOENT if
> +cur_key is the last key in the hash, or negative error in case of
> +failure.
> +
> +Examples
> +========
> +
> +Please see the ``tools/testing/selftests/bpf`` directory for functional
> +examples. This sample code demonstrates API usage.
[..]
> +Kernel
> +------
> +
> +.. code-block:: c
> +
> + #include <linux/bpf.h>
> + #include <bpf/bpf_helpers.h>
> +
> + struct key {
> + __u32 srcip;
> + };
> +
> + struct value {
> + __u64 packets;
> + __u64 bytes;
> + };
> +
> + struct {
> + __uint(type, BPF_MAP_TYPE_LRU_HASH);
> + __uint(max_entries, 32);
> + __type(key, struct key);
> + __type(value, struct value);
> + } packet_stats SEC(".maps");
> +
> + static inline void count_by_srcip(__u32 srcip, int bytes)
> + {
> + struct key key = {
> + .srcip = srcip
> + };
> + struct value *value = bpf_map_lookup_elem(&packet_stats,
> &key);
> + if (value) {
> + __sync_fetch_and_add(&value->packets, 1);
> + __sync_fetch_and_add(&value->bytes, bytes);
> + } else {
> + struct value newval = { 1, bytes };
> + bpf_map_update_elem(&packet_stats, &key, &newval,
> BPF_NOEXIST);
> + }
> + }
> +
> +Userspace
> +---------
> +
> +.. code-block:: c
> +
> + #include <bpf/libbpf.h>
> + #include <bpf/bpf.h>
> +
> + static void print_values(int map_fd)
> + {
> + struct key *cur_key = NULL;
> + struct key next_key;
> + int next;
> + do {
> + next = bpf_map_get_next_key(stats_fd, cur_key,
> &next_key);
> + if (next == -ENOENT)
> + break;
> + if (next < 0) {
> + fprintf(stderr, "bpf_map_get_next_key %d
> returned %s\n", stats_fd, strerror(-next));
> + break;
> + }
> +
> + struct in_addr src_addr = {
> + .s_addr = next_key.srcip
> + };
> + char *src_ip = inet_ntoa(src_addr);
> +
> + struct value value;
> + int ret = bpf_map_lookup_elem(stats_fd, &next_key,
> &value);
> + if (ret < 0) {
> + fprintf(stderr, "Failed to lookup elem with
> key %s: %s\n", src_ip, strerror(-ret));
> + break;
> + }
> + printf("%s: %lld packets, %lld bytes\n", src_ip,
> value.packets, value.bytes);
> + cur_key = &next_key;
> + } while (next == 0);
> + }
Instead of adding c code, maybe add pointers to specific file within
tools/testing/selftests/bpf/progs ? That's what we've done for
prog_cgroup_sockopt; the actual tests are a bit more maintained than
the doc :-)
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] bpf, docs: document BPF_MAP_TYPE_HASH and variants
2022-07-13 21:16 [PATCH] bpf, docs: document BPF_MAP_TYPE_HASH and variants Donald Hunter
2022-07-13 23:30 ` sdf
@ 2022-07-14 1:12 ` Bagas Sanjaya
2022-07-14 5:51 ` Daniel Müller
1 sibling, 1 reply; 7+ messages in thread
From: Bagas Sanjaya @ 2022-07-14 1:12 UTC (permalink / raw)
To: Donald Hunter, bpf, linux-doc; +Cc: Jonathan Corbet
On 7/14/22 04:16, Donald Hunter wrote:
> This commit adds documentation for BPF_MAP_TYPE_HASH including kernel
> version introduced, usage and examples. It also documents
> BPF_MAP_TYPE_PERCPU_HASH, BPF_MAP_TYPE_LRU_HASH and
> BPF_MAP_TYPE_LRU_PERCPU_HASH which are similar.
>
Please, please use imperative mood instead for patch description
(that is, better write like "document BPF_MAP_TYPE_* types").
--
An old man doll... just what I always wanted! - Clara
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] bpf, docs: document BPF_MAP_TYPE_HASH and variants
2022-07-14 1:12 ` Bagas Sanjaya
@ 2022-07-14 5:51 ` Daniel Müller
2022-07-14 8:10 ` Bagas Sanjaya
0 siblings, 1 reply; 7+ messages in thread
From: Daniel Müller @ 2022-07-14 5:51 UTC (permalink / raw)
To: Bagas Sanjaya; +Cc: Donald Hunter, bpf, linux-doc, Jonathan Corbet
On Thu, Jul 14, 2022 at 08:12:57AM +0700, Bagas Sanjaya wrote:
> On 7/14/22 04:16, Donald Hunter wrote:
> > This commit adds documentation for BPF_MAP_TYPE_HASH including kernel
> > version introduced, usage and examples. It also documents
> > BPF_MAP_TYPE_PERCPU_HASH, BPF_MAP_TYPE_LRU_HASH and
> > BPF_MAP_TYPE_LRU_PERCPU_HASH which are similar.
> >
>
> Please, please use imperative mood instead for patch description
> (that is, better write like "document BPF_MAP_TYPE_* types").
Can you elaborate why you make that recommendation, please?
Thanks,
Daniel
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] bpf, docs: document BPF_MAP_TYPE_HASH and variants
2022-07-14 5:51 ` Daniel Müller
@ 2022-07-14 8:10 ` Bagas Sanjaya
2022-07-14 21:53 ` Donald Hunter
0 siblings, 1 reply; 7+ messages in thread
From: Bagas Sanjaya @ 2022-07-14 8:10 UTC (permalink / raw)
To: Daniel Müller; +Cc: Donald Hunter, bpf, linux-doc, Jonathan Corbet
On 7/14/22 12:51, Daniel Müller wrote:
> On Thu, Jul 14, 2022 at 08:12:57AM +0700, Bagas Sanjaya wrote:
>> On 7/14/22 04:16, Donald Hunter wrote:
>>> This commit adds documentation for BPF_MAP_TYPE_HASH including kernel
>>> version introduced, usage and examples. It also documents
>>> BPF_MAP_TYPE_PERCPU_HASH, BPF_MAP_TYPE_LRU_HASH and
>>> BPF_MAP_TYPE_LRU_PERCPU_HASH which are similar.
>>>
>>
>> Please, please use imperative mood instead for patch description
>> (that is, better write like "document BPF_MAP_TYPE_* types").
>
> Can you elaborate why you make that recommendation, please?
>
From Documentation/process/submitting-patches.rst:
> Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
> instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
> to do frotz", as if you are giving orders to the codebase to change
> its behaviour.
The recommendation above is from commit 74a475acea4945
("SubmittingPatches: add style recommendation to use imperative descriptions")
Thanks.
--
An old man doll... just what I always wanted! - Clara
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] bpf, docs: document BPF_MAP_TYPE_HASH and variants
2022-07-14 8:10 ` Bagas Sanjaya
@ 2022-07-14 21:53 ` Donald Hunter
0 siblings, 0 replies; 7+ messages in thread
From: Donald Hunter @ 2022-07-14 21:53 UTC (permalink / raw)
To: Bagas Sanjaya; +Cc: Daniel Müller, bpf, linux-doc, Jonathan Corbet
Bagas Sanjaya <bagasdotme@gmail.com> writes:
>
> From Documentation/process/submitting-patches.rst:
>
>> Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
>> instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
>> to do frotz", as if you are giving orders to the codebase to change
>> its behaviour.
>
> The recommendation above is from commit 74a475acea4945
> ("SubmittingPatches: add style recommendation to use imperative descriptions")
>
> Thanks.
Thanks for the pointer. I will follow this guidance for v2.
Donald.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] bpf, docs: document BPF_MAP_TYPE_HASH and variants
2022-07-13 23:30 ` sdf
@ 2022-07-14 22:20 ` Donald Hunter
0 siblings, 0 replies; 7+ messages in thread
From: Donald Hunter @ 2022-07-14 22:20 UTC (permalink / raw)
To: sdf; +Cc: bpf, linux-doc, Jonathan Corbet
sdf@google.com writes:
>> +``BPF_MAP_TYPE_HASH`` and ``BPF_MAP_TYPE_PERCPU_HASH`` provide general
>> +purpose hash map storage. Both the key and the value can be structs,
>> +allowing for composite keys and values. The maximum number of entries is
>> +defined in max_entries and is limited to 2^32. The kernel is responsible
>
> Do we really need to mention 2^32 limit here? It really depends on
> the key/value sizes, right?
>
> Instead, might be worth talking about how/when this memory is allocated and
> mention BPF_F_NO_PREALLOC?
Good suggestion. I'll incorporate this into v2.
>> +.. c:function::
>> + long bpf_map_update_elem(struct bpf_map *map, const void *key, const void *value, u60
>> flags)
>
> s/u60/u64/
Good catch, thanks.
>> +Kernel
>> +------
>> +
>> +.. code-block:: c
>> +
>> + #include <linux/bpf.h>
>> + #include <bpf/bpf_helpers.h>
>> +
>> + struct key {
>> + __u32 srcip;
>> + };
>> +
>> + struct value {
>> + __u64 packets;
>> + __u64 bytes;
>> + };
>> +
>> + struct {
>> + __uint(type, BPF_MAP_TYPE_LRU_HASH);
>> + __uint(max_entries, 32);
>> + __type(key, struct key);
>> + __type(value, struct value);
>> + } packet_stats SEC(".maps");
>> +
>> + static inline void count_by_srcip(__u32 srcip, int bytes)
>> + {
>> + struct key key = {
>> + .srcip = srcip
>> + };
>> + struct value *value = bpf_map_lookup_elem(&packet_stats, &key);
>> + if (value) {
>> + __sync_fetch_and_add(&value->packets, 1);
>> + __sync_fetch_and_add(&value->bytes, bytes);
>> + } else {
>> + struct value newval = { 1, bytes };
>> + bpf_map_update_elem(&packet_stats, &key, &newval, BPF_NOEXIST);
>> + }
>> + }
>> +
>> +Userspace
>> +---------
>> +
>> +.. code-block:: c
>> +
>> + #include <bpf/libbpf.h>
>> + #include <bpf/bpf.h>
>> +
>> + static void print_values(int map_fd)
>> + {
>> + struct key *cur_key = NULL;
>> + struct key next_key;
>> + int next;
>> + do {
>> + next = bpf_map_get_next_key(stats_fd, cur_key, &next_key);
>> + if (next == -ENOENT)
>> + break;
>> + if (next < 0) {
>> + fprintf(stderr, "bpf_map_get_next_key %d returned %s\n",
>> stats_fd, strerror(-next));
>> + break;
>> + }
>> +
>> + struct in_addr src_addr = {
>> + .s_addr = next_key.srcip
>> + };
>> + char *src_ip = inet_ntoa(src_addr);
>> +
>> + struct value value;
>> + int ret = bpf_map_lookup_elem(stats_fd, &next_key, &value);
>> + if (ret < 0) {
>> + fprintf(stderr, "Failed to lookup elem with key %s: %s\n",
>> src_ip, strerror(-ret));
>> + break;
>> + }
>> + printf("%s: %lld packets, %lld bytes\n", src_ip, value.packets,
>> value.bytes);
>> + cur_key = &next_key;
>> + } while (next == 0);
>> + }
>
> Instead of adding c code, maybe add pointers to specific file within
> tools/testing/selftests/bpf/progs ? That's what we've done for
> prog_cgroup_sockopt; the actual tests are a bit more maintained than
> the doc :-)
I tried to cut the examples to the minimum that was still complete
enough to show use in context. Happy to try cutting the examples down to
a sequence of shorter snippets and and links to samples/bpf and
tools/testing/selftests/bpf/progs. I'll need to reference samples/bpf
because there are no bpf_map_get_next_key examples in
tools/testing/selftests/bpf/progs.
Donald.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2022-07-14 22:26 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-07-13 21:16 [PATCH] bpf, docs: document BPF_MAP_TYPE_HASH and variants Donald Hunter
2022-07-13 23:30 ` sdf
2022-07-14 22:20 ` Donald Hunter
2022-07-14 1:12 ` Bagas Sanjaya
2022-07-14 5:51 ` Daniel Müller
2022-07-14 8:10 ` Bagas Sanjaya
2022-07-14 21:53 ` Donald Hunter
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