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/*
Reading packets using fixed and dynamic buffer
Copyright (C) Amitay Isaacs 2015
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
/* This is similar to read_packet abstraction. The main different is that
* tevent fd event is created only once.
*/
#include "replace.h"
#include "system/network.h"
#include <talloc.h>
#include <tevent.h>
#include "lib/util/tevent_unix.h"
#include "pkt_read.h"
/*
* Read a packet using fixed buffer
*/
struct pkt_read_state {
int fd;
uint8_t *buf;
size_t buflen;
size_t nread, total;
bool use_fixed;
ssize_t (*more)(uint8_t *buf, size_t buflen, void *private_data);
void *private_data;
};
struct tevent_req *pkt_read_send(TALLOC_CTX *mem_ctx,
struct tevent_context *ev,
int fd, size_t initial,
uint8_t *buf, size_t buflen,
ssize_t (*more)(uint8_t *buf,
size_t buflen,
void *private_data),
void *private_data)
{
struct tevent_req *req;
struct pkt_read_state *state;
req = tevent_req_create(mem_ctx, &state, struct pkt_read_state);
if (req == NULL) {
return NULL;
}
state->fd = fd;
if (buf == NULL || buflen == 0) {
state->use_fixed = false;
state->buf = talloc_array(state, uint8_t, initial);
if (state->buf == NULL) {
talloc_free(req);
return NULL;
}
state->buflen = initial;
} else {
state->use_fixed = true;
state->buf = buf;
state->buflen = buflen;
}
state->nread = 0;
state->total = initial;
state->more = more;
state->private_data = private_data;
return req;
}
void pkt_read_handler(struct tevent_context *ev, struct tevent_fd *fde,
uint16_t flags, struct tevent_req *req)
{
struct pkt_read_state *state = tevent_req_data(
req, struct pkt_read_state);
ssize_t nread, more;
uint8_t *tmp;
nread = read(state->fd, state->buf + state->nread,
state->total - state->nread);
if ((nread == -1) && (errno == EINTR)) {
/* retry */
return;
}
if (nread == -1) {
tevent_req_error(req, errno);
return;
}
if (nread == 0) {
/* fd closed */
tevent_req_error(req, EPIPE);
return;
}
state->nread += nread;
if (state->nread < state->total) {
/* come back later */
return;
}
/* Check if "more" asks for more data */
if (state->more == NULL) {
tevent_req_done(req);
return;
}
more = state->more(state->buf, state->nread, state->private_data);
if (more == -1) {
/* invalid packet */
tevent_req_error(req, EIO);
return;
}
if (more == 0) {
tevent_req_done(req);
return;
}
if (state->total + more < state->total) {
/* int wrapped */
tevent_req_error(req, EMSGSIZE);
return;
}
if (state->total + more < state->buflen) {
/* continue using fixed buffer */
state->total += more;
return;
}
if (state->use_fixed) {
/* switch to dynamic buffer */
tmp = talloc_array(state, uint8_t, state->total + more);
if (tevent_req_nomem(tmp, req)) {
return;
}
memcpy(tmp, state->buf, state->total);
state->use_fixed = false;
} else {
tmp = talloc_realloc(state, state->buf, uint8_t,
state->total + more);
if (tevent_req_nomem(tmp, req)) {
return;
}
}
state->buf = tmp;
state->buflen = state->total + more;
state->total += more;
}
ssize_t pkt_read_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
uint8_t **pbuf, bool *free_buf, int *perrno)
{
struct pkt_read_state *state = tevent_req_data(
req, struct pkt_read_state);
if (tevent_req_is_unix_error(req, perrno)) {
return -1;
}
if (state->use_fixed) {
*pbuf = state->buf;
*free_buf = false;
} else {
*pbuf = talloc_steal(mem_ctx, state->buf);
*free_buf = true;
}
return state->total;
}
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