On Jul 1, 2017 9:01 AM, "Kirspel, Kevin" <kevin-kirs...@idexx.com> wrote:
I get a crash when running the tcpdump command in LIBBSD. It is due to the
following structure
struct stp_bpdu_ {
u_int8_t protocol_id[2];
u_int8_t protocol_version;
u_int8_t bpdu_type;
u_int8_t flags;
u_int8_t root_id[8];
u_int8_t root_path_cost[4];
u_int8_t bridge_id[8];
u_int8_t port_id[2];
u_int8_t message_age[2];
u_int8_t max_age[2];
u_int8_t hello_time[2];
u_int8_t forward_delay[2];
u_int8_t v1_length;
};
In the code, there is an access to the port_id field as follows:
EXTRACT_16BITS(&stp_bpdu->port_id). EXTRACT_16BITS calls ntohs() . Since
the address of “&stp_bpdu->port_id” is at an odd word (16 bit) boundary, an
exception is generated. What is the correct way to fix this? I was going
to update EXTRACT_16BITS to check for an odd boundary and fix it up before
calling ntohs().
There should be a bit in cp15 which determines is unaligned accesses are
enabled. Should be examples in other BSPs
--joel
Kevin Kirspel
Electrical Engineer - Sr. Staff
Idexx Roswell
235 Hembree Park Drive
Roswell GA 30076
Tel: (770)-510-4444 ext. 81642 <(770)%20510-4444>
Direct: (770)-688-1642 <(770)%20688-1642>
Fax: (770)-510-4445 <(770)%20510-4445>
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