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Add support for IPv6-only nameserver system configurations
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Signed-off-by: DL6ER <dl6er@dl6er.de>
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@DL6ER
DL6ER committed Jun 17, 2023
1 parent 61931f9 commit 3dcbaf7
Showing 1 changed file with 81 additions and 49 deletions.
130 changes: 81 additions & 49 deletions src/resolve.c
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Expand Up @@ -82,16 +82,17 @@ static void print_used_resolvers(const char *message)
return;

log_debug(DEBUG_RESOLVER, "%s", message);
for(int i = 0u; i < 2*MAXNS; i++)
const int num_ns4 = (sizeof(_res.nsaddr_list) / sizeof(_res.nsaddr_list[0]));
const int num_ns6 = (sizeof(_res._u._ext.nsaddrs) / sizeof(_res._u._ext.nsaddrs[0]));
for(int i = 0u; i < num_ns4 + num_ns6; i++)
{
int family;
in_port_t port;
void *addr = NULL;
int j = i;
if(i < MAXNS)
if(i < num_ns4)
{
// Regular name servers (IPv4)

const int j = i;
// Some of the entries may not be configured
if(i > _res.nscount || _res.nsaddr_list[j].sin_family != AF_INET)
continue;
Expand All @@ -104,7 +105,7 @@ static void print_used_resolvers(const char *message)
else
{
// Extension name servers (IPv6)
j = i - MAXNS;
const int j = i - num_ns4;
// Some of the entries may not be configured
if(_res._u._ext.nsaddrs[j] == NULL ||
_res._u._ext.nsaddrs[j]->sin6_family != AF_INET6)
Expand All @@ -119,7 +120,7 @@ static void print_used_resolvers(const char *message)
inet_ntop(family, addr, nsname, INET6_ADDRSTRLEN);

log_debug(DEBUG_RESOLVER, " %s %d: %s:%hu (IPv%u)", i < MAXNS ? " " : "EXT",
j, nsname, port, family == AF_INET ? 4u : 6u);
i, nsname, port, family == AF_INET ? 4u : 6u);
}
}

Expand Down Expand Up @@ -227,68 +228,99 @@ char *resolveHostname(const char *addr)
struct in_addr FTLaddr = { htonl(INADDR_LOOPBACK) };
in_port_t FTLport = htons(config.dns.port.v.u16);

// Set FTL as system resolver only if not already the primary resolver
if(_res.nsaddr_list[0].sin_addr.s_addr != FTLaddr.s_addr || _res.nsaddr_list[0].sin_port != FTLport)
// Temporarily set FTL as system resolver

// Backup configured name servers and invalidate them (IPv4)
struct in_addr ns_addr_bck[MAXNS];
in_port_t ns_port_bck[MAXNS];
int bck_nscount = _res.nscount;
for(int i = 0; i < bck_nscount; i++)
{
// Backup configured name servers and invalidate them
struct in_addr ns_addr_bck[MAXNS];
in_port_t ns_port_bck[MAXNS];
for(unsigned int i = 0u; i < MAXNS; i++)
{
ns_addr_bck[i] = _res.nsaddr_list[i].sin_addr;
ns_port_bck[i] = _res.nsaddr_list[i].sin_port;
_res.nsaddr_list[i].sin_addr.s_addr = 0; // 0.0.0.0
}
ns_addr_bck[i] = _res.nsaddr_list[i].sin_addr;
ns_port_bck[i] = _res.nsaddr_list[i].sin_port;
_res.nsaddr_list[i].sin_addr.s_addr = 0; // 0.0.0.0
}

// Set FTL at 127.0.0.1 as the only resolver
_res.nsaddr_list[0].sin_addr.s_addr = FTLaddr.s_addr;
// Set resolver port
_res.nsaddr_list[0].sin_port = FTLport;
// Configure resolver to use only one resolver
_res.nscount = 1;

// Backup configured name server and invalidate them (IPv6)
struct in6_addr ns6_addr_bck[MAXNS];
int bck_nscount6 = _res._u._ext.nscount6;
for(int i = 0; i < bck_nscount6; i++)
{
if(_res._u._ext.nsaddrs[i] == NULL)
continue;
memcpy(&ns6_addr_bck[i], &_res._u._ext.nsaddrs[i]->sin6_addr, sizeof(struct in6_addr));
memcpy(&_res._u._ext.nsaddrs[i]->sin6_addr, &in6addr_any, sizeof(struct in6_addr));
}

// Set FTL at 127.0.0.1 as the only resolver
_res.nsaddr_list[0].sin_addr.s_addr = FTLaddr.s_addr;
// Set FTL as the only resolver only when IPv6 is enabled
if(bck_nscount6 > 0)
{
// Set FTL at ::1 as the only resolver
memcpy(&_res._u._ext.nsaddrs[0]->sin6_addr, &in6addr_loopback, sizeof(struct in6_addr));
// Set resolver port
_res.nsaddr_list[0].sin_port = FTLport;
_res._u._ext.nsaddrs[0]->sin6_port = FTLport;
// Configure resolver to use only one resolver
_res._u._ext.nscount6 = 1;
}

if(config.debug.resolver.v.b)
print_used_resolvers("Setting nameservers to:");
if(config.debug.resolver.v.b)
print_used_resolvers("Set nameservers to:");

// Try to resolve address
char host[NI_MAXHOST] = { 0 };
int ret = getnameinfo((struct sockaddr*)&ss, sizeof(ss), host, sizeof(host), NULL, 0, NI_NAMEREQD);
// Try to resolve address
char host[NI_MAXHOST] = { 0 };
int ret = getnameinfo((struct sockaddr*)&ss, sizeof(ss), host, sizeof(host), NULL, 0, NI_NAMEREQD);

// Check if getnameinfo() returned a host name
if(ret == 0)
// Check if getnameinfo() returned a host name
if(ret == 0)
{
if(valid_hostname(host, addr))
{
if(valid_hostname(host, addr))
{
// Return hostname copied to new memory location
hostname = strdup(host);
}
else
{
hostname = strdup("[invalid host name]");
}

log_debug(DEBUG_RESOLVER, " ---> \"%s\" (found internally)", hostname);
// Return hostname copied to new memory location
hostname = strdup(host);
}
else
log_debug(DEBUG_RESOLVER, " ---> \"\" (not found internally: %s", gai_strerror(ret));
{
hostname = strdup("[invalid host name]");
}

log_debug(DEBUG_RESOLVER, " ---> \"%s\" (found internally)", hostname);
}
else
log_debug(DEBUG_RESOLVER, " ---> \"\" (not found internally: %s", gai_strerror(ret));

// Restore resolvers (without forced FTL)
for(unsigned int i = 0u; i < MAXNS; i++)
{
_res.nsaddr_list[i].sin_addr = ns_addr_bck[i];
_res.nsaddr_list[i].sin_port = ns_port_bck[i];
}
// Restore IPv4 resolvers
for(int i = 0; i < bck_nscount; i++)
{
_res.nsaddr_list[i].sin_addr = ns_addr_bck[i];
_res.nsaddr_list[i].sin_port = ns_port_bck[i];
}
else if(config.debug.resolver.v.b)
print_used_resolvers("FTL already primary nameserver:");
_res.nscount = bck_nscount;

// Restore IPv6 resolvers
for(int i = 0; i < bck_nscount6; i++)
{
if(_res._u._ext.nsaddrs[i] == NULL)
continue;
memcpy(&_res._u._ext.nsaddrs[i]->sin6_addr, &ns6_addr_bck[i], sizeof(struct in6_addr));
}
_res._u._ext.nscount6 = bck_nscount6;

if(config.debug.resolver.v.b)
print_used_resolvers("Restored nameservers to:");

// If no host name was found before, try again with system-configured
// resolvers (necessary for docker and friends)
if(hostname == NULL)
{
// Try to resolve address
char host[NI_MAXHOST] = { 0 };
int ret = getnameinfo((struct sockaddr*)&ss, sizeof(ss), host, sizeof(host), NULL, 0, NI_NAMEREQD);
ret = getnameinfo((struct sockaddr*)&ss, sizeof(ss), host, sizeof(host), NULL, 0, NI_NAMEREQD);

// Check if getnameinfo() returned a host name this time
// First check for he not being NULL before trying to dereference it
Expand Down

1 comment on commit 3dcbaf7

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This commit has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/query-log-does-not-show-hostnames-from-pihole-dhcp/63344/28

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