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net: telnet: Improve command processing

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Current TELNET implementation wrongly assumed that if the command is
present, it will always be included at the beginning of the packet/data
buffer. Such assumptions however are not valid for STREAM sockets,
where the actual stream data could be fragmented in any way.

Therefore, the command parsing needed rework, so that we analyze each
byte received for the command escape code, and once received we enter
"command parsing" mode. Once no more commands are identified in a data
streak, the command bytes are removed from the data buffer before the
buffer is provided to the shell subsystem for processing.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>
This commit is contained in:
Robert Lubos 2024-02-29 13:35:52 +01:00 • committed by David Leach
commit 5bb97a112d
2 changed files with 83 additions and 23 deletions
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3
include/zephyr/shell/shell_telnet.h
View file

@ -17,6 +17,7 @@ extern "C" {
extern const struct shell_transport_api shell_telnet_transport_api;
#define SHELL_TELNET_POLLFD_COUNT 3
#define SHELL_TELNET_MAX_CMD_SIZE 3
/** Line buffer structure. */
struct shell_telnet_line_buf {
@ -49,6 +50,8 @@ struct shell_telnet {
/** Mutex protecting the input buffer access. */
struct k_mutex rx_lock;
uint8_t cmd_buf[SHELL_TELNET_MAX_CMD_SIZE];
uint8_t cmd_len;
/** The delayed work is used to send non-lf terminated output that has
* been around for "too long". This will prove to be useful

103
subsys/shell/backends/shell_telnet.c
View file

@ -236,13 +236,19 @@ static void telnet_send_prematurely(struct k_work *work)
}
}
static inline int telnet_handle_command(uint8_t *buf)
static int telnet_command_length(uint8_t op)
{
if (op == NVT_CMD_SB || op == NVT_CMD_WILL || op == NVT_CMD_WONT ||
op == NVT_CMD_DO || op == NVT_CMD_DONT) {
return TELNET_WILL_DO_COMMAND_LEN;
}
return TELNET_MIN_COMMAND_LEN;
}
static inline int telnet_handle_command(struct telnet_simple_command *cmd)
{
/* Commands are two or three bytes. */
struct telnet_simple_command *cmd;
cmd = (struct telnet_simple_command *)buf;
if (cmd->iac != NVT_CMD_IAC) {
return 0;
}
@ -257,17 +263,14 @@ static inline int telnet_handle_command(uint8_t *buf)
return -EOPNOTSUPP;
}
if (cmd->op == NVT_CMD_WILL || cmd->op == NVT_CMD_WONT ||
cmd->op == NVT_CMD_DO || cmd->op == NVT_CMD_DONT) {
return TELNET_WILL_DO_COMMAND_LEN;
}
return TELNET_MIN_COMMAND_LEN;
return 0;
}
static void telnet_recv(struct zsock_pollfd *pollfd)
{
size_t len, off, buf_left;
struct telnet_simple_command *cmd =
(struct telnet_simple_command *)sh_telnet->cmd_buf;
size_t len, off, buf_left, cmd_total_len;
uint8_t *buf;
int ret;
@ -294,18 +297,70 @@ static void telnet_recv(struct zsock_pollfd *pollfd)
off = 0;
len = ret;
while (len >= TELNET_MIN_COMMAND_LEN) {
ret = telnet_handle_command(buf + off);
if (ret > 0) {
LOG_DBG("Handled command");
off += ret;
} else if (ret < 0) {
goto error;
} else {
break;
cmd_total_len = 0;
/* Filter out and process commands from the data buffer. */
while (off < len) {
if (sh_telnet->cmd_len > 0) {
/* Command mode */
if (sh_telnet->cmd_len == 1) {
/* Operation */
cmd->op = *(buf + off);
sh_telnet->cmd_len++;
cmd_total_len++;
off++;
if (telnet_command_length(cmd->op) >
TELNET_MIN_COMMAND_LEN) {
continue;
}
} else if (sh_telnet->cmd_len == 2) {
/* Option */
cmd->opt = *(buf + off);
sh_telnet->cmd_len++;
cmd_total_len++;
off++;
}
ret = telnet_handle_command(cmd);
if (ret < 0) {
goto error;
} else {
LOG_DBG("Handled command");
}
memset(cmd, 0, sizeof(*cmd));
sh_telnet->cmd_len = 0;
continue;
}
len -= ret;
if (*(buf + off) == NVT_CMD_IAC) {
cmd->iac = *(buf + off);
sh_telnet->cmd_len++;
cmd_total_len++;
off++;
continue;
}
/* Data byte, remove command bytes from the buffer, if any. */
if (cmd_total_len > 0) {
size_t data_off = off;
off -= cmd_total_len;
len -= cmd_total_len;
cmd_total_len = 0;
memmove(buf + off, buf + data_off, len);
}
off++;
}
if (cmd_total_len > 0) {
/* In case the buffer ended with command, trim the buffer size
* here.
*/
len -= cmd_total_len;
}
if (len == 0) {
@ -313,7 +368,6 @@ static void telnet_recv(struct zsock_pollfd *pollfd)
return;
}
memmove(buf, buf + off, len);
sh_telnet->rx_len += len;
k_mutex_unlock(&sh_telnet->rx_lock);
@ -376,6 +430,9 @@ static void telnet_accept(struct zsock_pollfd *pollfd)
sh_telnet->fds[SOCK_ID_CLIENT].fd = sock;
sh_telnet->fds[SOCK_ID_CLIENT].events = ZSOCK_POLLIN;
sh_telnet->rx_len = 0;
sh_telnet->cmd_len = 0;
sh_telnet->line_out.len = 0;
ret = net_socket_service_register(&telnet_server, sh_telnet->fds,
ARRAY_SIZE(sh_telnet->fds), NULL);