On Nov 11, 2009, at 2:00 AM, Mohacsi Janos wrote:
I think this try_and_success_or_failure method can work in most
cases, however it has some burden for implementation and operational
point of view,
It does indeed, at least operationally. That is trivially solved for
sites one frequently visits, using a cache - if one finds that address
pair {source, destination} works one time, one might try it first next
time.
As to the implementation, I have written the code for the naive
version on Linux (and then threw it away for some reason), and it's
not too hard. It comes down to
get all of my addresses
get all his addresses
for each address pair in some order
"connect" on the socket
do {
"select" for K ms or a result, whichever comes first
} while (result was a connection attempt failing)
if result was a connection succeeding, break
}
// at this point we have an open connection or some outstanding
while (we have no open connection and some connection attempts in
progress) {
"select" seeking a result
}
if (we have a connection open) {
for each connection attempt except that one {
close it
}
}
return the connected socket
Ideally, if one wishes to have a properly designed socket interface,
one puts that in a subroutine that one calls with a name and gets
either a connected socket or a failure in response, so that the
application knows nothing about IP addresses (see UNSAF). But now I am
engaging in wishful thinking - that the socket interface would be
reasonably designed.
Caching implies some form of storage, which probably involves a kernel
API, which I have not tried to prototype.
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