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/* lib9p/9p.h - Base 9P protocol definitions for both clients and servers
*
* Copyright (C) 2024 Luke T. Shumaker <lukeshu@lukeshu.com>
* SPDX-Licence-Identifier: AGPL-3.0-or-later
*/
#ifndef _LIB9P_9P_H_
#define _LIB9P_9P_H_
#include <assert.h>
#include <stdbool.h>
#include <sys/types.h> /* for ssize_t */
#include <lib9p/linux-errno.h>
/* configuration **************************************************************/
#include "config.h"
#ifndef CONFIG_9P_MAX_ERR_SIZE
# error config.h must define CONFIG_9P_MAX_ERR_SIZE
#endif
#ifndef CONFIG_9P_ENABLE_9P2000
# define CONFIG_9P_ENABLE_9P2000
#endif
/******************************************************************************/
#include <lib9p/9p.generated.h> /* *after* config.h */
#define LIB9P_NOTAG ((uint16_t)~0U)
#define LIB9P_NOFID ((uint32_t)~0U)
struct lib9p_ctx {
/* negotiated */
enum lib9p_version version;
uint32_t max_msg_size;
/* state */
uint32_t err_num;
char err_msg[CONFIG_9P_MAX_ERR_SIZE];
};
static void lib9p_ctx_clear_error(struct lib9p_ctx *ctx) {
assert(ctx);
ctx->err_num = 0;
ctx->err_msg[0] = '\0';
}
static bool lib9p_ctx_has_error(struct lib9p_ctx *ctx) {
assert(ctx);
return ctx->err_num || ctx->err_msg[0];
}
/** Write an static error into ctx, return -1. */
int lib9p_error(struct lib9p_ctx *ctx, uint32_t linux_errno, char const *msg);
/** Write a printf-style error into ctx, return -1. */
int lib9p_errorf(struct lib9p_ctx *ctx, uint32_t linux_errno, char const *fmt, ...);
/**
* Validate a message's structure; it's size, string encodings, enums,
* and bitfields.
*
* Return how much space the message will take when unmarshaled. This
* number may be larger than net_bytes due to (1) struct padding, (2)
* nul-terminator bytes for strings.
*
* Emits an error (return -1, set ctx->err_num and ctx->err_msg) if
* either the message type is unknown, or if net_bytes is too short
* for that message type, or if an invalid string (invalid UTF-8,
* contains a nul-byte) is encountered.
*
* @param net_bytes : the complete request, starting with the "size[4]"
*
* @return required size, or -1 on error
*
* @errno LINUX_EOPNOTSUPP: message has unknown type
* @errno LINUX_EBADMSG: message is wrong size for content
* @errno LINUX_EBADMSG: message contains invalid UTF-8
* @errno LINUX_EBADMSG: message contains a bitfield with unknown bits
* @errno LINUX_EMSGSIZE: would-be return value overflows SSIZE_MAX
*/
ssize_t lib9p_validate(struct lib9p_ctx *ctx, uint8_t *net_bytes);
/**
* Unmarshal the 9P message `net_bytes` into the C struct `ret_body`.
*
* Emits an error (return 0, set ctx->err_num and ctx->err_msg) if a
* string contains invalid UTF-8 or a nul-byte.
*
* lib9p_unmarshal does no validation; you must run lib9p_validate()
* first.
*
* @param ctx : negotiated protocol parameters, where to record errors
* @param net_bytes : the complete message, starting with the "size[4]"
*
* @return ret_typ : the mesage type
* @return ret_body : the message body, must be at least lib9p_validate() bytes
*/
void lib9p_unmarshal(struct lib9p_ctx *ctx, uint8_t *net_bytes,
enum lib9p_msg_type *ret_typ, void *ret_body);
/**
* Marshal a `struct lib9p_msg_{typ}` structure into a byte-array.
*
* lib9p_marshal does no validation; it trusts that the programmer
* won't give it garbage input. However, just as it doesn't marshal
* struct fields that aren't in ctx->version, it won't marshal
* bitfield bits that aren't in ctx->version; it applies a
* version-specific mask to bitfields.
*
* @param ctx : negotiated protocol parameters, where to record errors
* @param typ : the message type
* @param msg : the message to encode
*
* @return ret_bytes : the buffer to encode to, must be at be at least lib9p_ctx_max_msg_size(ctx) bytes
* @return whether there was an error (false=success, true=error)
*
* @errno LINUX_ERANGE: reply does not fit in ctx->max_msg_size
*/
bool lib9p_marshal(struct lib9p_ctx *ctx, enum lib9p_msg_type typ, void *body,
uint8_t *ret_bytes);
#endif _LIB9P_9P_H_
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