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resolve: Maintain order of DNS servers also when installing in resolv.conf

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This always writes the complete set of DNS servers to make modifications
simpler.
This commit is contained in:
Tobias Brunner 2023-06-16 13:46:17 +02:00
parent 6440975bb4
commit 8238ad480a
1 changed files with 30 additions and 50 deletions
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80
src/libcharon/plugins/resolve/resolve_handler.c
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@ -32,6 +32,9 @@
/* default interface/protocol used for resolvconf (should have high prio) */
#define RESOLVCONF_IFACE "lo.ipsec"
/* suffix added to lines in resolv.conf */
#define RESOLV_CONF_SUFFIX " # by strongSwan"
typedef struct private_resolve_handler_t private_resolve_handler_t;
/**
@ -106,13 +109,15 @@ static bool dns_server_equals(const void *a, const void *b)
}
/**
* Writes the given nameserver to resolv.conf
* Writes the given nameservers to resolv.conf
*/
static bool write_nameserver(private_resolve_handler_t *this, host_t *addr)
static bool write_nameservers(private_resolve_handler_t *this,
hashtable_t *servers)
{
FILE *in, *out;
char buf[1024];
size_t len;
enumerator_t *enumerator;
dns_server_t *dns;
char line[1024];
bool handled = FALSE;
in = fopen(this->file, "r");
@ -121,18 +126,28 @@ static bool write_nameserver(private_resolve_handler_t *this, host_t *addr)
out = fopen(this->file, "w");
if (out)
{
fprintf(out, "nameserver %H # by strongSwan\n", addr);
DBG1(DBG_IKE, "installing DNS server %H to %s", addr, this->file);
handled = TRUE;
/* write our current set of servers */
enumerator = servers->create_enumerator(servers);
while (enumerator->enumerate(enumerator, NULL, &dns))
{
fprintf(out, "nameserver %H" RESOLV_CONF_SUFFIX "\n", dns->server);
}
enumerator->destroy(enumerator);
/* copy rest of the file */
if (in)
{
while ((len = fread(buf, 1, sizeof(buf), in)))
/* copy the rest of the file, except our previous servers */
while (fgets(line, sizeof(line), in))
{
ignore_result(fwrite(buf, 1, len, out));
if (!strstr(line, RESOLV_CONF_SUFFIX "\n"))
{
fputs(line, out);
}
}
}
handled = TRUE;
fclose(out);
}
if (in)
@ -142,44 +157,6 @@ static bool write_nameserver(private_resolve_handler_t *this, host_t *addr)
return handled;
}
/**
* Removes the given nameserver from resolv.conf
*/
static void remove_nameserver(private_resolve_handler_t *this, host_t *addr)
{
FILE *in, *out;
char line[1024], matcher[512];
in = fopen(this->file, "r");
if (in)
{
/* allows us to stream from in to out */
unlink(this->file);
out = fopen(this->file, "w");
if (out)
{
snprintf(matcher, sizeof(matcher),
"nameserver %H # by strongSwan\n", addr);
/* copy all, but matching line */
while (fgets(line, sizeof(line), in))
{
if (strpfx(line, matcher))
{
DBG1(DBG_IKE, "removing DNS server %H from %s",
addr, this->file);
}
else
{
fputs(line, out);
}
}
fclose(out);
}
fclose(in);
}
}
/**
* Install the given nameservers by invoking resolvconf. If the table is empty,
* remove the config.
@ -303,7 +280,8 @@ METHOD(attribute_handler_t, handle, bool,
}
else
{
handled = write_nameserver(this, addr);
DBG1(DBG_IKE, "installing DNS server %H to %s", addr, this->file);
handled = write_nameservers(this, this->servers);
}
if (!handled)
{
@ -372,7 +350,9 @@ METHOD(attribute_handler_t, release, void,
}
else
{
remove_nameserver(this, addr);
DBG1(DBG_IKE, "removing DNS server %H from %s", addr,
this->file);
write_nameservers(this, this->servers);
}
}
}