Re: [PATCH 2/2] util: introduce virSocketAddrParseAny

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On 03/29/2018 11:27 AM, John Ferlan wrote:


On 03/26/2018 04:29 PM, Jim Fehlig wrote:
When preparing for migration, the libxl driver creates a new TCP listen
socket for the incoming migration by calling virNetSocketNewListenTCP,
passing the destination host name. virNetSocketNewListenTCP calls
virSocketAddrParse to check if the host name is a wildcard address, in
which case it avoids adding the AI_ADDRCONFIG flag to the hints passed to
getaddrinfo. If the host name is not an IP address, virSocketAddrParse
reports an error

error : virSocketAddrParseInternal:121 : Cannot parse socket address
'myhost.example.com': Name or service not known

But virNetSocketNewListenTCP succeeds regardless and the overall migration
operation succeeds.

Introduce virSocketAddrParseAny and use it when simply testing if a host
name/addr is parsable.

Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
---

Essentially a V2 of

https://www.redhat.com/archives/libvir-list/2018-March/msg01120.html

It takes a slightly different approach by creating a function that can
parse host names or IP addresses.

  src/libvirt_private.syms |  1 +
  src/rpc/virnetsocket.c   |  2 +-
  src/util/virsocketaddr.c | 50 +++++++++++++++++++++++++++++++++++++++++++++---
  src/util/virsocketaddr.h |  5 +++++
  4 files changed, 54 insertions(+), 4 deletions(-)


Reviewed-by: John Ferlan <jferlan@xxxxxxxxxx>

Wait for 4.2.0 for this one...

John

BTW: Your call on whether to add to the new API comments something about
the API could be susceptible to a delay due to network name resolution
lookup pause.  That is, from the getaddrinfo man page:

"The AI_NUMERICHOST flag suppresses any potentially lengthy network host
address lookups."

Good point. I squashed in the below comment to this patch before pushing both.

Regards,
Jim

diff --git a/src/util/virsocketaddr.c b/src/util/virsocketaddr.c
index 84610560f..99dc54830 100644
--- a/src/util/virsocketaddr.c
+++ b/src/util/virsocketaddr.c
@@ -173,7 +173,10 @@ int virSocketAddrParse(virSocketAddrPtr addr, const char *val, int family)
  *
  * Mostly a wrapper for getaddrinfo() extracting the address storage
  * from a host name like acme.example.com or a numeric string like 1.2.3.4
- * or 2001:db8:85a3:0:0:8a2e:370:7334
+ * or 2001:db8:85a3:0:0:8a2e:370:7334.
+ *
+ * When @val is a network host name, this function may be susceptible to a
+ * delay due to potentially lengthy netork host address lookups.
  *
  * Returns the length of the network address or -1 in case of error.
  */

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