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slirp: Read host DNS config on demand

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Currently the qemu user-mode networking stack reads the host DNS
configuration (/etc/resolv.conf or the Windows equivalent) only once
when qemu starts.  This causes name lookups in the guest to fail if the
host is moved to a different network from which the original DNS servers
are unreachable, a common occurrence when the host is a laptop.

This patch changes the slirp code to read the host DNS configuration on
demand, caching the results for at most 1 second to avoid unnecessary
overhead if name lookups occur in rapid succession.  On non-Windows
hosts, /etc/resolv.conf is re-read only if the file has been replaced or
if its size or mtime has changed.

Signed-off-by: Ed Swierk <eswierk@aristanetworks.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Ed Swierk 2009-08-20 19:00:31 -07:00 • committed by Anthony Liguori
parent ce0bd027df
commit df7a86ed73
6 changed files with 44 additions and 14 deletions
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3
slirp/tcp_subr.c
View file

@ -340,7 +340,8 @@ int tcp_fconnect(struct socket *so)
slirp->vnetwork_addr.s_addr) {
/* It's an alias */
if (so->so_faddr.s_addr == slirp->vnameserver_addr.s_addr) {
addr.sin_addr = dns_addr;
if (get_dns_addr(&addr.sin_addr) < 0)
addr.sin_addr = loopback_addr;
} else {
addr.sin_addr = loopback_addr;
}