mirror of
https://github.com/troglobit/finit.git
synced 2026-10-10 16:52:39 +07:00
Joachim Wiberg
b55dada80b
libink was written against the only bus it had, its own, where the peer on the other end is the client. A broker is not: it routes for senders it names itself, expects a DESTINATION on anything addressed through it, and answers on its own schedule rather than next. Runlevels go on the wire as S and N rather than the digits Finit keeps internally, since that is what a caller outside Finit means by one. The library stays a convenience library, linked into finit and initctl and installed nowhere: the ABI promise waits until libink is its own project. Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
104 lines
3.4 KiB
C
104 lines
3.4 KiB
C
/* libink — D-Bus wire protocol: message header parsing and building.
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*
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* Copyright (c) 2026 Joachim Wiberg <troglobit@gmail.com>
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* SPDX-License-Identifier: MIT
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*/
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#ifndef LIBINK_PROTO_H_
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#define LIBINK_PROTO_H_
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#include <stddef.h>
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#include <stdint.h>
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#include <stdbool.h>
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#include "link.h" /* LINK_MSG_* type codes */
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/* Message flags. */
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#define LINK_FLAG_NO_REPLY_EXPECTED 0x01
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#define LINK_FLAG_NO_AUTO_START 0x02
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#define LINK_FLAG_ALLOW_INTERACTIVE_AUTHORIZATION 0x04
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/* Header field codes. */
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#define LINK_HDR_PATH 1
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#define LINK_HDR_INTERFACE 2
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#define LINK_HDR_MEMBER 3
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#define LINK_HDR_ERROR_NAME 4
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#define LINK_HDR_REPLY_SERIAL 5
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#define LINK_HDR_DESTINATION 6
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#define LINK_HDR_SENDER 7
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#define LINK_HDR_SIGNATURE 8
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#define LINK_HDR_UNIX_FDS 9
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#define LINK_PROTOCOL_VERSION 1
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/* Parsed view of an incoming message. Pointers reference bytes
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* inside the receiver's own rx buffer; treat as borrowed and short-
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* lived (until the next read of the same connection). */
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struct link_msg {
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uint8_t type;
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uint8_t flags;
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uint8_t endian; /* 'l' or 'B' */
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uint32_t body_len;
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uint32_t serial;
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uint32_t reply_serial;
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const char *path; /* object path, or NULL */
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const char *interface; /* may be NULL on method calls */
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const char *member;
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const char *error_name;
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const char *destination;
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const char *sender;
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const char *signature; /* may be NULL if body is empty */
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/* Pointer into the rx buffer and length, after header padding. */
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const uint8_t *body;
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uint32_t body_avail;
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};
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/* Parse a complete D-Bus message from `buf` of size `len`. On
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* success returns the total number of bytes consumed (header +
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* padding + body) and fills *out. Returns 0 if more bytes are
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* needed, -1 on malformed input. */
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ssize_t __msg_parse(const uint8_t *buf, size_t len, struct link_msg *out);
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/* Compute the on-wire size of a future message header given the
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* fields we'd populate. Used to size send buffers. */
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size_t __msg_header_size(const struct link_msg *m);
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/* Build a method-return header into `buf` (capacity `cap`).
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* `reply_serial`/`destination` come from the call being replied to.
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* `signature` is the body signature ("" if no args). `body_len`
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* is the length of the body that will follow the header padding.
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* Returns the number of bytes written, or -1 on overflow. */
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ssize_t __msg_build_return(uint8_t *buf, size_t cap,
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uint32_t serial, uint32_t reply_serial,
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const char *destination,
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const char *signature, uint32_t body_len);
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/* Build an error reply header. */
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ssize_t __msg_build_error(uint8_t *buf, size_t cap,
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uint32_t serial, uint32_t reply_serial,
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const char *destination,
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const char *error_name,
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const char *signature, uint32_t body_len);
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/* Build a signal header (no reply expected, no destination). */
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ssize_t __msg_build_signal(uint8_t *buf, size_t cap,
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uint32_t serial,
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const char *path,
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const char *interface,
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const char *member,
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const char *signature, uint32_t body_len);
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/* Build a method-call header (client side). `destination` is NULL
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* when no broker routes the message. */
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ssize_t __msg_build_method_call(uint8_t *buf, size_t cap,
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uint32_t serial,
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const char *path,
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const char *interface,
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const char *member,
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const char *destination,
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const char *signature,
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uint32_t body_len);
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#endif /* LIBINK_PROTO_H_ */
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