[Asterisk-Dev] struct q931_ie

[Schaefer, Mark]

I'll try this again...

In the libpri source tree, there is the following code in pri_q931.h

/* Information element format */
typedef struct q931_ie {
#if __BYTE_ORDER == __BIG_ENDIAN
	u_int8_t f:1;
	u_int8_t ie:7;
#else
	u_int8_t ie:7;
	u_int8_t f:1;
#endif
	u_int8_t len;
	u_int8_t data[0];
} q931_ie;

I believe this code is incorrect.  Here's why:

In q931.c, the following code exists:

		if (!(ie->ie & 0xf0) && (y < 0))
		    mandies[MAX_MAND_IES - 1] = ie->ie;

If the length of ie is 7 bits instead of the normal 8 bits, then that
comparison should be 0x70.  The same problem is exhibited when the following
might be received as a valid information element:

#define Q931_LOCKING_SHIFT			0x90

In the current code, that ie will never be parsed.

Suggest you change the code to:

typedef struct q931_ie {
	u_int8_t ie:8;
	u_int8_t len;
	u_int8_t data[0];
} q931_ie;

	Anywhere you look for ie->f, you can replace it with ie->ie & 0x80,
which does not break endianness.

BTW: The #define above is incorrect.  Q931_LOCKING_SHIFT is 0x90 through
0x97 from what I've seen.  Asterisk barfs on any locking shift due to some
poor coding.

Later,

Mark Schaefer
OnStar Corporation