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Tell the truth about DNS lookups in the Event Log.

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We've always had the back-end code unconditionally print 'Looking up
host' before calling name_lookup. But name_lookup doesn't always do an
actual lookup - in cases where the connection will be proxied and
we're configured to let the proxy do the DNS for us, it just calls
sk_nonamelookup to return a dummy SockAddr with the unresolved name
still in it. It's better to print a message that varies depending on
whether we're _really_ doing DNS or not, e.g. so that people can tell
the difference between DNS failure and proxy misconfiguration.

Hence, those log messages are now generated inside name_lookup(),
which takes a couple of extra parameters for the purpose - a frontend
pointer to pass to logevent(), and a reason string so that it can say
what the hostname it's (optionally) looking up is going to be used
for. (The latter is intended for possible use in logging subsidiary
lookups for port forwarding, though  the moment I haven't changed
the current setup where those connection setups aren't logged in
detail - we just pass NULL in that situation.)
This commit is contained in:
Simon Tatham 2015-11-22 09:58:14 +00:00
parent 42334b65b0
commit 37cdfdcd51
8 changed files with 37 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
network.h
View File

@ -100,7 +100,8 @@ Socket new_connection(SockAddr addr, const char *hostname,
Socket new_listener(const char *srcaddr, int port, Plug plug,
int local_host_only, Conf *conf, int addressfamily);
SockAddr name_lookup(const char *host, int port, char **canonicalname,
Conf *conf, int addressfamily);
Conf *conf, int addressfamily, void *frontend_for_logging,
const char *lookup_reason_for_logging);
int proxy_for_destination (SockAddr addr, const char *hostname, int port,
Conf *conf);

3
portfwd.c
View File

@ -443,7 +443,8 @@ char *pfd_connect(struct PortForwarding **pf_ret, char *hostname,int port,
/*
* Try to find host.
*/
addr = name_lookup(hostname, port, &dummy_realhost, conf, addressfamily);
addr = name_lookup(hostname, port, &dummy_realhost, conf, addressfamily,
NULL, NULL);
if ((err = sk_addr_error(addr)) != NULL) {
char *err_ret = dupstr(err);
sk_addr_free(addr);

25
proxy.c
View File

@ -363,16 +363,35 @@ int proxy_for_destination (SockAddr addr, const char *hostname,
}
SockAddr name_lookup(const char *host, int port, char **canonicalname,
Conf *conf, int addressfamily)
Conf *conf, int addressfamily, void *frontend,
const char *reason)
{
char *logmsg;
if (conf_get_int(conf, CONF_proxy_type) != PROXY_NONE &&
do_proxy_dns(conf) &&
proxy_for_destination(NULL, host, port, conf)) {
if (frontend) {
logmsg = dupprintf("Leaving host lookup to proxy of \"%s\""
" (for %s)", host, reason);
logevent(frontend, logmsg);
sfree(logmsg);
}
*canonicalname = dupstr(host);
return sk_nonamelookup(host);
}
} else {
if (frontend) {
logmsg = dupprintf("Looking up host \"%s\"%s for %s", host,
(addressfamily == ADDRTYPE_IPV4 ? " (IPv4)" :
addressfamily == ADDRTYPE_IPV6 ? " (IPv6)" :
""), reason);
logevent(frontend, logmsg);
sfree(logmsg);
}
return sk_namelookup(host, canonicalname, addressfamily);
return sk_namelookup(host, canonicalname, addressfamily);
}
}
Socket new_connection(SockAddr addr, const char *hostname,

12
raw.c
View File

@ -154,16 +154,8 @@ static const char *raw_init(void *frontend_handle, void **backend_handle,
/*
* Try to find host.
*/
{
char *buf;
buf = dupprintf("Looking up host \"%s\"%s", host,
(addressfamily == ADDRTYPE_IPV4 ? " (IPv4)" :
(addressfamily == ADDRTYPE_IPV6 ? " (IPv6)" :
"")));
logevent(raw->frontend, buf);
sfree(buf);
}
addr = name_lookup(host, port, realhost, conf, addressfamily);
addr = name_lookup(host, port, realhost, conf, addressfamily,
raw->frontend, "main connection");
if ((err = sk_addr_error(addr)) != NULL) {
sk_addr_free(addr);
return err;

12
rlogin.c
View File

@ -194,16 +194,8 @@ static const char *rlogin_init(void *frontend_handle, void **backend_handle,
/*
* Try to find host.
*/
{
char *buf;
buf = dupprintf("Looking up host \"%s\"%s", host,
(addressfamily == ADDRTYPE_IPV4 ? " (IPv4)" :
(addressfamily == ADDRTYPE_IPV6 ? " (IPv6)" :
"")));
logevent(rlogin->frontend, buf);
sfree(buf);
}
addr = name_lookup(host, port, realhost, conf, addressfamily);
addr = name_lookup(host, port, realhost, conf, addressfamily,
rlogin->frontend, "rlogin connection");
if ((err = sk_addr_error(addr)) != NULL) {
sk_addr_free(addr);
return err;

6
ssh.c
View File

@ -3674,10 +3674,8 @@ static const char *connect_to_host(Ssh ssh, const char *host, int port,
* Try to find host.
*/
addressfamily = conf_get_int(ssh->conf, CONF_addressfamily);
logeventf(ssh, "Looking up host \"%s\"%s", host,
(addressfamily == ADDRTYPE_IPV4 ? " (IPv4)" :
(addressfamily == ADDRTYPE_IPV6 ? " (IPv6)" : "")));
addr = name_lookup(host, port, realhost, ssh->conf, addressfamily);
addr = name_lookup(host, port, realhost, ssh->conf, addressfamily,
ssh->frontend, "SSH connection");
if ((err = sk_addr_error(addr)) != NULL) {
sk_addr_free(addr);
return err;

14
telnet.c
View File

@ -751,17 +751,9 @@ static const char *telnet_init(void *frontend_handle, void **backend_handle,
/*
* Try to find host.
*/
{
char *buf;
addressfamily = conf_get_int(telnet->conf, CONF_addressfamily);
buf = dupprintf("Looking up host \"%s\"%s", host,
(addressfamily == ADDRTYPE_IPV4 ? " (IPv4)" :
(addressfamily == ADDRTYPE_IPV6 ? " (IPv6)" :
"")));
logevent(telnet->frontend, buf);
sfree(buf);
}
addr = name_lookup(host, port, realhost, telnet->conf, addressfamily);
addressfamily = conf_get_int(telnet->conf, CONF_addressfamily);
addr = name_lookup(host, port, realhost, telnet->conf, addressfamily,
telnet->frontend, "Telnet connection");
if ((err = sk_addr_error(addr)) != NULL) {
sk_addr_free(addr);
return err;

3
x11fwd.c
View File

@ -286,7 +286,8 @@ struct X11Display *x11_setup_display(const char *display, Conf *conf)
disp->port = 6000 + disp->displaynum;
disp->addr = name_lookup(disp->hostname, disp->port,
&disp->realhost, conf, ADDRTYPE_UNSPEC);
&disp->realhost, conf, ADDRTYPE_UNSPEC,
NULL, NULL);
if ((err = sk_addr_error(disp->addr)) != NULL) {
sk_addr_free(disp->addr);