Bug 61538 – [UNIX] SOCK_DGRAM sockets are not notified when the other end closes the connection

• Component: WebKit2
• Status: RESOLVED FIXED

[Carlos Garcia Campos]

A possible solution to this problem is to use SOCK_SEQPACKET instead of SOCK_DGRAM, but it's linux-only, see bug #61287 for more details. So, even if we decice to use SOCK_SEQPACKET when available we still need an implementation when it isn't. The problem of not being notified when the other end closes the connection is that the process might get blocked waiting for a sync reply that will never be received because the other process has closed the connection. This currently happens when the web process sends the DestroyPlugin message to the plugin process and it was the las plugin. In that case the plugin process closes the connection and finishes after a timeout. During that timeout the web process is waiting for the reply to the DestroyPlugin message, and it doesn't wake uo until the plugin process really dies.

[Carlos Garcia Campos]

Created attachment 94986 [details]
Patch to use STREAM sockets

One of the possible solutions would be simply using STREAM sockets instead of DGRAM sockets when SEQPACKET is not available. The problem is that the code is more complex because we need to handle message boundaries in the receiver, but the same code works for SEQPACKET sockets too.

[Anders Carlsson]

Comment on attachment 94986 [details]
Patch to use STREAM sockets

View in context: https://bugs.webkit.org/attachment.cgi?id=94986&action=review

> Source/WebKit2/Platform/CoreIPC/unix/ConnectionUnix.cpp:334
> +        // Process messages from data received.
> +        while (processMessage()) { }

I think this reads better as

while (true) {
    if (!processMessage())
      break;
}

[Carlos Garcia Campos]

Committed r88147: <http://trac.webkit.org/changeset/88147>