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Some updates to mention accept filters and how

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listen queues work in a syncache world.

MFC after:	3 days
This commit is contained in:
silby 2002-05-08 18:19:01 +00:00
parent f379586992
commit 2f7396a747
2 changed files with 33 additions and 2 deletions
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5
lib/libc/sys/accept.2
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@ -115,6 +115,10 @@ request and not implying confirmation.
Confirmation can be implied by a normal read or write on the new
file descriptor, and rejection can be implied by closing the
new socket.
.Pp
For some applications, performance may be enhanced by using an
.Xr accept_filter 9
to pre-process incoming connections.
.Sh RETURN VALUES
The call returns \-1 on error. If it succeeds, it returns a non-negative
integer that is a descriptor for the accepted socket.
@ -151,6 +155,7 @@ A connection arrived, but it was closed while waiting
on the listen queue.
.El
.Sh SEE ALSO
.Xr accept_filter 9 ,
.Xr bind 2 ,
.Xr connect 2 ,
.Xr getpeername 2 ,

30
lib/libc/sys/listen.2
View File

@ -70,8 +70,20 @@ If a connection
request arrives with the queue full the client may
receive an error with an indication of
.Er ECONNREFUSED ,
or, if the underlying protocol supports retransmission,
the request may be ignored so that retries may succeed.
or, in the case of TCP, the connection will be
silently dropped.
.Pp
Note that before FreeBSD 4.5 and the introduction of the syncache,
the
.Fa backlog
parameter also determined the length of the incomplete
connection queue, which held TCP sockets in the process
of completing TCP's 3-way handshake. These incomplete connections
are now held entirely in the syncache, which is unaffected by
queue lengths. Inflated
.Fa backlog
values to help handle denial
of service attacks are no longer necessary.
.Pp
The
.Xr sysctl 3
@ -85,6 +97,19 @@ or less than zero is specified,
.Fa backlog
is silently forced to
.Va kern.ipc.somaxconn .
.Sh INTERACTION WITH ACCEPT FILTERS
When accept filtering is used on a socket, a second queue will
be used to hold sockets that have connected, but have not yet
met their accept filtering criteria. Once the criteria has been
met, these sockets will be moved over into the completed connection
queue to be accept()ed. If this secondary queue is full and a
new connection comes in, the oldest socket which has not yet met
its accept filter criteria will be terminated.
.Pp
This secondary queue, like the primary listen queue, is sized
according to the
.Fa backlog
parameter.
.Sh RETURN VALUES
.Rv -std listen
.Sh ERRORS
@ -105,6 +130,7 @@ The socket is not of a type that supports the operation
.El
.Sh SEE ALSO
.Xr accept 2 ,
.Xr accept_filter 9 ,
.Xr connect 2 ,
.Xr socket 2 ,
.Xr sysctl 3 ,