bpf: fix minor issues in documentation for BPF helpers.

This commit brings many minor fixes to the documentation for BPF helper
functions. Mostly, this is limited to formatting fixes and improvements.
In particular, fix broken formatting for bpf_skb_adjust_room().

Besides formatting, replace the mention of "bpf_fullsock()" (that is not
associated with any function or type exposed to the user) in the
description of bpf_sk_storage_get() by "full socket".
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

include/uapi/linux/bpf.h

@@ -1518,18 +1518,18 @@ union bpf_attr {
  *		* **BPF_F_ADJ_ROOM_FIXED_GSO**: Do not adjust gso_size.
  *		  Adjusting mss in this way is not allowed for datagrams.
  *
- *		* **BPF_F_ADJ_ROOM_ENCAP_L3_IPV4 **:
- *		* **BPF_F_ADJ_ROOM_ENCAP_L3_IPV6 **:
+ *		* **BPF_F_ADJ_ROOM_ENCAP_L3_IPV4**,
+ *		  **BPF_F_ADJ_ROOM_ENCAP_L3_IPV6**:
  *		  Any new space is reserved to hold a tunnel header.
  *		  Configure skb offsets and other fields accordingly.
  *
- *		* **BPF_F_ADJ_ROOM_ENCAP_L4_GRE **:
- *		* **BPF_F_ADJ_ROOM_ENCAP_L4_UDP **:
+ *		* **BPF_F_ADJ_ROOM_ENCAP_L4_GRE**,
+ *		  **BPF_F_ADJ_ROOM_ENCAP_L4_UDP**:
  *		  Use with ENCAP_L3 flags to further specify the tunnel type.
  *
- *		* **BPF_F_ADJ_ROOM_ENCAP_L2(len) **:
+ *		* **BPF_F_ADJ_ROOM_ENCAP_L2**\ (*len*):
  *		  Use with ENCAP_L3/L4 flags to further specify the tunnel
- *		  type; **len** is the length of the inner MAC header.
+ *		  type; *len* is the length of the inner MAC header.
  *
  * 		A call to this helper is susceptible to change the underlying
  * 		packet buffer. Therefore, at load time, all checks on pointers
@@ -2061,16 +2061,16 @@ union bpf_attr {
  *		**BPF_LWT_ENCAP_IP**
  *			IP encapsulation (GRE/GUE/IPIP/etc). The outer header
  *			must be IPv4 or IPv6, followed by zero or more
- *			additional headers, up to LWT_BPF_MAX_HEADROOM total
- *			bytes in all prepended headers. Please note that
- *			if skb_is_gso(skb) is true, no more than two headers
- *			can be prepended, and the inner header, if present,
- *			should be either GRE or UDP/GUE.
+ *			additional headers, up to **LWT_BPF_MAX_HEADROOM**
+ *			total bytes in all prepended headers. Please note that
+ *			if **skb_is_gso**\ (*skb*) is true, no more than two
+ *			headers can be prepended, and the inner header, if
+ *			present, should be either GRE or UDP/GUE.
  *
- *		BPF_LWT_ENCAP_SEG6*** types can be called by bpf programs of
- *		type BPF_PROG_TYPE_LWT_IN; BPF_LWT_ENCAP_IP type can be called
- *		by bpf programs of types BPF_PROG_TYPE_LWT_IN and
- *		BPF_PROG_TYPE_LWT_XMIT.
+ *		**BPF_LWT_ENCAP_SEG6**\ \* types can be called by BPF programs
+ *		of type **BPF_PROG_TYPE_LWT_IN**; **BPF_LWT_ENCAP_IP** type can
+ *		be called by bpf programs of types **BPF_PROG_TYPE_LWT_IN** and
+ *		**BPF_PROG_TYPE_LWT_XMIT**.
  *
  * 		A call to this helper is susceptible to change the underlying
  * 		packet buffer. Therefore, at load time, all checks on pointers
@@ -2126,11 +2126,11 @@ union bpf_attr {
  *			Type of *param*: **int**.
  *		**SEG6_LOCAL_ACTION_END_B6**
  *			End.B6 action: Endpoint bound to an SRv6 policy.
- *			Type of param: **struct ipv6_sr_hdr**.
+ *			Type of *param*: **struct ipv6_sr_hdr**.
  *		**SEG6_LOCAL_ACTION_END_B6_ENCAP**
  *			End.B6.Encap action: Endpoint bound to an SRv6
  *			encapsulation policy.
- *			Type of param: **struct ipv6_sr_hdr**.
+ *			Type of *param*: **struct ipv6_sr_hdr**.
  *
  * 		A call to this helper is susceptible to change the underlying
  * 		packet buffer. Therefore, at load time, all checks on pointers
@@ -2285,7 +2285,8 @@ union bpf_attr {
  *	Return
  *		Pointer to **struct bpf_sock**, or **NULL** in case of failure.
  *		For sockets with reuseport option, the **struct bpf_sock**
- *		result is from **reuse->socks**\ [] using the hash of the tuple.
+ *		result is from *reuse*\ **->socks**\ [] using the hash of the
+ *		tuple.
  *
  * struct bpf_sock *bpf_sk_lookup_udp(void *ctx, struct bpf_sock_tuple *tuple, u32 tuple_size, u64 netns, u64 flags)
  *	Description
@@ -2321,7 +2322,8 @@ union bpf_attr {
  *	Return
  *		Pointer to **struct bpf_sock**, or **NULL** in case of failure.
  *		For sockets with reuseport option, the **struct bpf_sock**
- *		result is from **reuse->socks**\ [] using the hash of the tuple.
+ *		result is from *reuse*\ **->socks**\ [] using the hash of the
+ *		tuple.
  *
  * int bpf_sk_release(struct bpf_sock *sock)
  *	Description
@@ -2490,31 +2492,34 @@ union bpf_attr {
  *		network namespace *netns*. The return value must be checked,
  *		and if non-**NULL**, released via **bpf_sk_release**\ ().
  *
- *		This function is identical to bpf_sk_lookup_tcp, except that it
- *		also returns timewait or request sockets. Use bpf_sk_fullsock
- *		or bpf_tcp_socket to access the full structure.
+ *		This function is identical to **bpf_sk_lookup_tcp**\ (), except
+ *		that it also returns timewait or request sockets. Use
+ *		**bpf_sk_fullsock**\ () or **bpf_tcp_sock**\ () to access the
+ *		full structure.
  *
  *		This helper is available only if the kernel was compiled with
  *		**CONFIG_NET** configuration option.
  *	Return
  *		Pointer to **struct bpf_sock**, or **NULL** in case of failure.
  *		For sockets with reuseport option, the **struct bpf_sock**
- *		result is from **reuse->socks**\ [] using the hash of the tuple.
+ *		result is from *reuse*\ **->socks**\ [] using the hash of the
+ *		tuple.
  *
  * int bpf_tcp_check_syncookie(struct bpf_sock *sk, void *iph, u32 iph_len, struct tcphdr *th, u32 th_len)
  * 	Description
- * 		Check whether iph and th contain a valid SYN cookie ACK for
- * 		the listening socket in sk.
+ * 		Check whether *iph* and *th* contain a valid SYN cookie ACK for
+ * 		the listening socket in *sk*.
  *
- * 		iph points to the start of the IPv4 or IPv6 header, while
- * 		iph_len contains sizeof(struct iphdr) or sizeof(struct ip6hdr).
+ * 		*iph* points to the start of the IPv4 or IPv6 header, while
+ * 		*iph_len* contains **sizeof**\ (**struct iphdr**) or
+ * 		**sizeof**\ (**struct ip6hdr**).
  *
- * 		th points to the start of the TCP header, while th_len contains
- * 		sizeof(struct tcphdr).
+ * 		*th* points to the start of the TCP header, while *th_len*
+ * 		contains **sizeof**\ (**struct tcphdr**).
  *
  * 	Return
- * 		0 if iph and th are a valid SYN cookie ACK, or a negative error
- * 		otherwise.
+ * 		0 if *iph* and *th* are a valid SYN cookie ACK, or a negative
+ * 		error otherwise.
  *
  * int bpf_sysctl_get_name(struct bpf_sysctl *ctx, char *buf, size_t buf_len, u64 flags)
  *	Description
@@ -2592,17 +2597,17 @@ union bpf_attr {
  *		and save the result in *res*.
  *
  *		The string may begin with an arbitrary amount of white space
- *		(as determined by isspace(3)) followed by a single optional '-'
- *		sign.
+ *		(as determined by **isspace**\ (3)) followed by a single
+ *		optional '**-**' sign.
  *
  *		Five least significant bits of *flags* encode base, other bits
  *		are currently unused.
  *
  *		Base must be either 8, 10, 16 or 0 to detect it automatically
- *		similar to user space strtol(3).
+ *		similar to user space **strtol**\ (3).
  *	Return
  *		Number of characters consumed on success. Must be positive but
- *		no more than buf_len.
+ *		no more than *buf_len*.
  *
  *		**-EINVAL** if no valid digits were found or unsupported base
  *		was provided.
@@ -2616,16 +2621,16 @@ union bpf_attr {
  *		given base and save the result in *res*.
  *
  *		The string may begin with an arbitrary amount of white space
- *		(as determined by isspace(3)).
+ *		(as determined by **isspace**\ (3)).
  *
  *		Five least significant bits of *flags* encode base, other bits
  *		are currently unused.
  *
  *		Base must be either 8, 10, 16 or 0 to detect it automatically
- *		similar to user space strtoul(3).
+ *		similar to user space **strtoul**\ (3).
  *	Return
  *		Number of characters consumed on success. Must be positive but
- *		no more than buf_len.
+ *		no more than *buf_len*.
  *
  *		**-EINVAL** if no valid digits were found or unsupported base
  *		was provided.
@@ -2634,26 +2639,26 @@ union bpf_attr {
  *
  * void *bpf_sk_storage_get(struct bpf_map *map, struct bpf_sock *sk, void *value, u64 flags)
  *	Description
- *		Get a bpf-local-storage from a sk.
+ *		Get a bpf-local-storage from a *sk*.
  *
  *		Logically, it could be thought of getting the value from
  *		a *map* with *sk* as the **key**.  From this
  *		perspective,  the usage is not much different from
- *		**bpf_map_lookup_elem(map, &sk)** except this
- *		helper enforces the key must be a **bpf_fullsock()**
- *		and the map must be a BPF_MAP_TYPE_SK_STORAGE also.
+ *		**bpf_map_lookup_elem**\ (*map*, **&**\ *sk*) except this
+ *		helper enforces the key must be a full socket and the map must
+ *		be a **BPF_MAP_TYPE_SK_STORAGE** also.
  *
  *		Underneath, the value is stored locally at *sk* instead of
- *		the map.  The *map* is used as the bpf-local-storage **type**.
- *		The bpf-local-storage **type** (i.e. the *map*) is searched
- *		against all bpf-local-storages residing at sk.
+ *		the *map*.  The *map* is used as the bpf-local-storage
+ *		"type". The bpf-local-storage "type" (i.e. the *map*) is
+ *		searched against all bpf-local-storages residing at *sk*.
  *
- *		An optional *flags* (BPF_SK_STORAGE_GET_F_CREATE) can be
+ *		An optional *flags* (**BPF_SK_STORAGE_GET_F_CREATE**) can be
  *		used such that a new bpf-local-storage will be
  *		created if one does not exist.  *value* can be used
- *		together with BPF_SK_STORAGE_GET_F_CREATE to specify
+ *		together with **BPF_SK_STORAGE_GET_F_CREATE** to specify
  *		the initial value of a bpf-local-storage.  If *value* is
- *		NULL, the new bpf-local-storage will be zero initialized.
+ *		**NULL**, the new bpf-local-storage will be zero initialized.
  *	Return
  *		A bpf-local-storage pointer is returned on success.
  *
@@ -2662,7 +2667,7 @@ union bpf_attr {
  *
  * int bpf_sk_storage_delete(struct bpf_map *map, struct bpf_sock *sk)
  *	Description
- *		Delete a bpf-local-storage from a sk.
+ *		Delete a bpf-local-storage from a *sk*.
  *	Return
  *		0 on success.
  *