Currently DNS resolution of SocketAddress structs is done as part of the socket connect/listen process. This is very inflexible as it assumes that a single SocketAddress struct will only ever require a single socket to be opened. While true for connect(), it is not the case for listen() in two scenarios
- A name may resolve to both an IPv4 and IPv6 address. Currently we workaround that by clearing the IPV6_V6ONLY flag. - A name may resolve to multiple IP addresses of the same protocol. eg "myhostname" may return "192.168.122.1" and "10.0.0.2" when the host has multiple NICs, or multiple addresses per NIC. The only way to deal with the latter problem is to open multiple sockets and that requires the ability to separate DNS resolution from socket creation. This series thus enhances the I/O framework in QEMU to introduce the "QIODNSResolver" concept. This (singleton) object allows the caller to feed in a single SocketAddress struct, perform DNS resolution, and get back out one or more new SocketAddress structs for the results. The API allows both synchronous and asynchrounous DNS lookups, the latter done by spawning a thread to do the getaddrinfo call via the QIOTask framework. In this series the InetSocketAddress struct gains a new field to let the caller indicate that the address is providing a numeric host value, thus skipping DNS altogether. The QIOTask object had some refactoring to allow results to be associated with it explicitly, so that the asynchronous DNS results can be passed around. This triggered the code churn across other files in QEMU using QIOTask. This series will be utilized by a second series that will be sent that updates the VNC server code to use this new feature. Daniel P. Berrange (8): sockets: add ability to disable DNS resolution for InetSocketAddress io: stop incrementing reference in qio_task_get_source io: fix typo in docs for QIOTask io: add ability to associate an opaque "result" with with a task io: add ability to associate an error with a task io: change the QIOTask callback signature io: remove Error parameter from QIOTask thread worker io: introduce a DNS resolver API include/io/dns-resolver.h | 224 ++++++++++++++++++++++++++++++++++ include/io/task.h | 151 ++++++++++++++++------- include/qemu/sockets.h | 2 + io/Makefile.objs | 1 + io/channel-socket.c | 50 ++++---- io/channel-tls.c | 16 +-- io/channel-websock.c | 8 +- io/dns-resolver.c | 265 +++++++++++++++++++++++++++++++++++++++++ io/task.c | 62 +++++++--- io/trace-events | 1 - migration/socket.c | 11 +- migration/tls.c | 19 +-- nbd/common.c | 8 +- nbd/nbd-internal.h | 3 +- qapi-schema.json | 5 + qemu-char.c | 18 +-- tests/test-io-channel-socket.c | 5 +- tests/test-io-channel-tls.c | 5 +- tests/test-io-task.c | 31 ++--- ui/vnc-auth-vencrypt.c | 7 +- ui/vnc-ws.c | 14 ++- util/qemu-sockets.c | 7 +- 22 files changed, 745 insertions(+), 168 deletions(-) create mode 100644 include/io/dns-resolver.h create mode 100644 io/dns-resolver.c -- 2.9.3
