Custom mg_set_non_blocking_mode() implementation

[dmitry-kandiner]

It would be nice to have an option for custom mg_set_non_blocking_mode() implementation - some architectures have non-standard way for doing so. For instance, Cyclone TCP stack implementation of fcntl() requires three parameters: a socket, a command and a pointer to the command parameters.

[cpq]

@dmitry-kandiner thank you!

Do you get a build error about it? If yes, could you share it please?

[dmitry-kandiner]

@cpq sure, here is the snippet from the build log:

...../mongoose.c: In function 'mg_set_non_blocking_mode':
...../mongoose.c:2981:22: error: too few arguments to function 'fcntl'
2981 | fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK); // Set non-blocking mode
| ^~~~~
In file included from ...../mongoose_custom.h:6,
from ...../mongoose.h:134,
from ...../mongoose.c:18:
...../core/bsd_socket.h:320:7: note: declared here
320 | int_t fcntl(int_t s, int_t cmd, void *arg);
| ^~~~~
...../mongoose.c:2982:13: error: 'F_SETFD' undeclared (first use in this function); did you mean 'F_SETFL'?
2982 | fcntl(fd, F_SETFD, FD_CLOEXEC); // Set close-on-exec
| ^~~~~~~
| F_SETFL
...../mongoose.c:2982:13: note: each undeclared identifier is reported only once for each function it appears in
...../mongoose.c:2982:22: error: 'FD_CLOEXEC' undeclared (first use in this function)
2982 | fcntl(fd, F_SETFD, FD_CLOEXEC); // Set close-on-exec
| ^~~~~~~~~~
Besides, Cyclone TCP stack does not define F_SETFD and FD_CLOEXEC.

Actually, my solution for this was like this:

2977: fcntl(fd, F_SETFL, O_NONBLOCK);
2978: #elif defined(mg_custom_set_non_blocking_mode)
2979: mg_custom_set_non_blocking_mode(fd);
2980: #else
2981: fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK); // Set non-blocking mode

Plus the following code in mongoose_cusom.h:

static inline void set_non_blocking_mode(int_t socket) {
uint32_t opt = O_NONBLOCK;
fcntl(socket, F_SETFL, &opt);
}
#define mg_custom_set_non_blocking_mode(fd) set_non_blocking_mode(fd)

Best regards,
Dmitry

[cpq]

Thank you.

Maybe a way to go is to create your own custom fcntl and define dummy values for F_SETFL and FD_CLOEXEC. Like, in your mongoose_custom.h, you can do something like this:

#define fcntl sys_fcntl

.....includes....


// Here make our own fcntl()
#define F_SETFD 12345
#define FD_CLOEXEC 0

#undef fcntl

static inline int fcntl(int fd, int cmd, ...) {
  if (cmd == F_GETFL) return sys_fcntl(fd, cmd);
  if (cmd == F_SETFL) {
    va_list ap;
    va_start(ap, cmd);
    uint32_t opt = va_arg(ap, int);
    int result = sys_fcntl(fd, cmd, &opt);
    va_end(ap);
    return result;
  }
  return 0;
}

[dmitry-kandiner]

Unfortunately, it didn't work for me. I tried to add the following code to the mogoose_custom.h, but was not able to link it.

#define fcntl sys_fcntl

#include <core/bsd_socket.h>

static inline int_t mg_fcntl(int_t fd, int_t cmd, void* opt)
{
	return sys_fcntl(fd, cmd, opt);
}

#define F_SETFD 12345
#define FD_CLOEXEC 0

#undef fcntl

static inline int fcntl(int fd, int cmd, ...) {
	if (cmd == F_GETFL) 
	{
		uint32_t opt;
		mg_fcntl(fd, cmd, &opt);
		return opt;
	}
	if (cmd == F_SETFL)
	{
		va_list ap;
		va_start(ap, cmd);
		uint32_t opt = va_arg(ap, int);
		int result = mg_fcntl(fd, cmd, &opt);
		va_end(ap);
		return result;
	}
	return 0;
}

Unfortunately linker fails with undefined reference to 'sys_fcntl'

[dmitry-kandiner]

Maybe the best way will be to use mg_fcntl() instead of fcntl() in case of MG_ARCH_CUSTOM, and let the user define it in mogoose_custom.h? Also, it is possible to use fcntl() as the fallback option if mg_fcntl() is not defined.

[cpq]

I still think it is possible to inject a custom fcntl() without code modification. How about this mongoose_custom.h:

#include <core/bsd_socket.h>

#define F_SETFD 12345
#define FD_CLOEXEC 0

static inline int mg_fcntl(int fd, int cmd, ...) {
  if (cmd == F_GETFL) { uint32_t opt; fcntl(fd, cmd, &opt); return opt; }
  ...
}

#define fcntl mg_fcntl

[dmitry-kandiner]

Thank you, @cpq , this solution worked for me!