Student Student - 1 month ago 14
Linux Question

How to receive bpdu traffic using raw socket in Linux C

How to get packets using

recvfrom()
? And how to know is it bdpu traffic?
I read somesource but didn't find listen ethernet traffic.

int data_size, addr_size;
char reply[6000];
struct sockaddr_in addr;

addr_size = sizeof addr;
datasize = recvfrom(sock, reply, 6000, 0, &addr, &addr_size);

if(data_size<0)
{
printf("nothing recv");
}
printf("%x",reply);


Output:

651a7ec0


What is this? I don't know.

Answer

the reply variable is a pointer to a 6000 byte array. When recvfrom returns, if fills this array with datasize bytes. To see the content, iterate over reply from index 0, until datasize:

for(i=0;i<datasize;i++)
{
    printf("%02x ",reply[i]);
}

I suggest declaring reply as unsinged char reply[6000].

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