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/* lib9p/9p.c - Base 9P protocol utilities for both clients and servers
*
* Copyright (C) 2024 Luke T. Shumaker <lukeshu@lukeshu.com>
* SPDX-Licence-Identifier: AGPL-3.0-or-later
*/
#include <inttypes.h> /* for PRIu{n} */
#include <stdarg.h> /* for va_* */
#include <stdio.h> /* for vsnprintf() */
#include <string.h> /* for strncpy() */
#include <lib9p/9p.h>
#include "internal.h"
int lib9p_error(struct lib9p_ctx *ctx, uint32_t linux_errno, char const *msg) {
strncpy(ctx->err_msg, msg, sizeof(ctx->err_msg));
ctx->err_msg[sizeof(ctx->err_msg)-1] = '\0';
ctx->err_num = linux_errno;
return -1;
}
int lib9p_errorf(struct lib9p_ctx *ctx, uint32_t linux_errno, char const *fmt, ...) {
int n;
va_list args;
va_start(args, fmt);
n = vsnprintf(ctx->err_msg, sizeof(ctx->err_msg), fmt, args);
va_end(args);
if ((size_t)(n+1) < sizeof(ctx->err_msg))
memset(&ctx->err_msg[n+1], 0, sizeof(ctx->err_msg)-(n+1));
ctx->err_num = linux_errno;
return -1;
}
ssize_t lib9p_validate(struct lib9p_ctx *ctx, uint8_t *net_bytes) {
/* Inspect the first 5 bytes ourselves. */
struct _validate_ctx subctx = {
.ctx = ctx,
.net_size = decode_u32le(net_bytes),
.net_bytes = net_bytes,
.net_offset = 0,
.host_extra = 0,
};
if (subctx.net_size < 5)
return lib9p_error(ctx, LINUX_EBADMSG, "message is impossibly short");
uint8_t typ = net_bytes[4];
struct _vtable_msg vtable = _lib9p_vtables[ctx->version].msgs[typ];
if (!vtable.validate)
return lib9p_errorf(ctx, LINUX_EOPNOTSUPP, "unknown message type: %s (protocol_version=%s)",
lib9p_msg_type_str(typ), lib9p_version_str(ctx->version));
/* Now use the message-type-specific vtable to process the whole thing. */
if (vtable.validate(&subctx))
return -1;
assert(subctx.net_offset <= subctx.net_size);
if (subctx.net_offset < subctx.net_size)
return lib9p_errorf(ctx, LINUX_EBADMSG, "message has %"PRIu32" extra bytes",
subctx.net_size - subctx.net_offset);
/* Return. */
ssize_t ret;
if (__builtin_add_overflow(vtable.basesize, subctx.host_extra, &ret))
return lib9p_error(ctx, LINUX_EMSGSIZE, "unmarshalled payload overflows SSIZE_MAX");
return ret;
}
void lib9p_unmarshal(struct lib9p_ctx *ctx, uint8_t *net_bytes,
enum lib9p_msg_type *ret_typ, void *ret_body) {
struct _unmarshal_ctx subctx = {
.ctx = ctx,
.net_bytes = net_bytes,
.net_offset = 0,
};
*ret_typ = net_bytes[4];
struct _vtable_msg vtable = _lib9p_vtables[ctx->version].msgs[*ret_typ];
subctx.extra = ret_body + vtable.basesize;
vtable.unmarshal(&subctx, ret_body);
}
bool lib9p_marshal(struct lib9p_ctx *ctx, enum lib9p_msg_type typ, void *body,
uint8_t *ret_bytes) {
struct _marshal_ctx subctx = {
.ctx = ctx,
.net_bytes = ret_bytes,
.net_offset = 0,
};
struct _vtable_msg vtable = _lib9p_vtables[ctx->version].msgs[typ];
return vtable.marshal(&subctx, body);
}
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