Re: [lwip-devel] Question on comparations of sequence numbers

[address@hidden]

narke wrote:
>    #define TCP_SEQ_LEQ(a,b)    ((s32_t)((a)-(b))<= 0)
>    #define TCP_SEQ_GEQ(a,b)    ((s32_t)((a)-(b))>= 0)
>
> so it means, a is within [b, c] iif
>
>   b<= a<= c
In window-numbers, your example is correct, but not in integer arithmetic.
> However, because sequence number cycles (module 2**32), so I cannot
> understand why a - b>=  0 mean  a>= b or a - c<= 0 means a<= c.
> For example, in a 2 bit window, and a window could be [3, 1] and 0
> falls in the window.  But here 3<= 0<= 1 does not hold.
I'm not sure I understand your example numbers. Should 3 be the smallest 
sequence number and 1 be the highest sequence number? How can that be if 
the biggest possible window size is 65535? If you meant it the other way 
round, 0 is outside of the window, isn't it?

Simon