Difference between revisions of "Sockets"
(dgram sockets are supported) |
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== Unix sockets initial support == | == Unix sockets initial support == | ||
| − | Currently it can only work with stream sockets, which have no skbs in queues | + | Currently it can only work with stream and dgram sockets, which have no skbs in queues |
(listening or established -- both work OK). If there are skbs in queue the dumping | (listening or established -- both work OK). If there are skbs in queue the dumping | ||
procedure will fail. | procedure will fail. | ||
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case. Currently it simply doesn't work :( | case. Currently it simply doesn't work :( | ||
| − | |||
* Need to add support for in-flight connections | * Need to add support for in-flight connections | ||
* Implement support for UDP sockets (quite simple) | * Implement support for UDP sockets (quite simple) | ||
* Implement support for listening TCP sockets (also not very complex) | * Implement support for listening TCP sockets (also not very complex) | ||
* Implement support for connected TCP scokets (hard one) | * Implement support for connected TCP scokets (hard one) | ||
Revision as of 20:01, 13 January 2012
Unix sockets initial support
Currently it can only work with stream and dgram sockets, which have no skbs in queues (listening or established -- both work OK). If there are skbs in queue the dumping procedure will fail.
The cpt part uses the sock_diag engine that was merged to Dave recently to collect sockets. Then it dumps sockets by checking the filesystem ID of a failed-to-open through /proc/pid/fd descriptors (sockets do not allow for such tricks with opens through proc) against SOCKFS_TYPE.
The restore part is more tricky. Listen sockets are just restored, this is simple. Connected sockets are restored like this:
- One end establishes a listening anon socket at the desired descriptor;
- The other end just creates a socket at the desired descriptor;
- All sockets, that are to be connect()-ed call connect. Unix sockets do not block connect() till the accept() time and thus we continue with...
- ... all listening sockets call accept() and ... dup2 the new fd into the accepting end.
There's a problem with this approach -- socket names are not preserved, but looking into our OpenVZ implementation I think this is OK for existing apps.
What should be done next
- Need to merge the file IDs patches in our tree and make Andrey to support files sharing. This will solve the
sk = socket();
fork();
case. Currently it simply doesn't work :(
- Need to add support for in-flight connections
- Implement support for UDP sockets (quite simple)
- Implement support for listening TCP sockets (also not very complex)
- Implement support for connected TCP scokets (hard one)