[PATCH 5/5] c/r: Add AF_UNIX support (v6)
orenl at librato.com
Tue Aug 4 01:27:27 PDT 2009
Dan Smith wrote:
> OL> Hmm.. then what happens when you have a circular dependency ? For
> OL> example, three dgram sockets, A, B and C where: A->B, B->C and
> OL> C->A ('->' means connected).
> So, I've been cooking up changes to the patch and a test for this
> case. However, it seems like it's not valid, unless I'm missing
> something. The man page for connect() says:
> If the socket sockfd is of type SOCK_DGRAM then serv_addr is the
> address to which datagrams are sent by default, and the only address
> from which datagrams are received.
> So, even though you can connect() a DGRAM socket and then sendto()
> datagrams to a different location, it doesn't appear that the
> relationship between A and B is really valid, at least the connection
> between A and B is not functional. In fact, in my testing, if you try
> to connect() C back to A, you get "Operation not permitted" because A
> is already connected elsewhere.
Weird ... I have a faint memory of seeing that happen (which is
why I brought it up).
Does this mean that a situation of A->B and B->C is valid only as
long as A->B is done first, otherwise A->B will fail because B will
already be connected to C ?
Then, the other problem is to restore correctly you need to mimic
the behavior of sendto() because of the way the skb references the
original socket for the write-buf accounting :(
In turn, this means that during checkpoint you need to record the
_origin_ of each buffer in the queue of afunix dgram sockets :((
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