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Add support for conditional domain suffices in HOSTNAMEFQDN mode #1250

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Nov 30, 2021
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Add support for conditional domain suffices in HOSTNAMEFQDN mode #1250

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94 changes: 66 additions & 28 deletions src/dnsmasq_interface.c
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,7 @@ static void alladdr_extract_ip(union all_addr *addr, const sa_family_t family, c
static void check_pihole_PTR(char *domain);
#define query_set_dnssec(query, dnssec) _query_set_dnssec(query, dnssec, __FILE__, __LINE__)
static void _query_set_dnssec(queriesData *query, const enum dnssec_status dnssec, const char *file, const int line);
static char *get_ptrname(struct in_addr *addr);

// Static blocking metadata
static const char *blockingreason = "";
Expand Down Expand Up @@ -1060,6 +1061,23 @@ static void check_pihole_PTR(char *domain)
// The last PTR record in daemon->ptr is reserved for Pi-hole
free(pihole_ptr->name);
pihole_ptr->name = strdup(domain);
if(family == AF_INET)
{
// IPv4 supports conditional domains
struct in_addr addrv4 = { 0 };
addrv4.s_addr = iface->addr.in.sin_addr.s_addr;
pihole_ptr->ptr = get_ptrname(&addrv4);
}
else
{
// IPv6 does not support conditional domains
pihole_ptr->ptr = get_ptrname(NULL);
}

// Debug logging
if(config.debug & DEBUG_QUERIES)
logg("Generating PTR response: %s -> %s", pihole_ptr->name, pihole_ptr->ptr);

return;
}
}
Expand Down Expand Up @@ -2765,7 +2783,35 @@ void FTL_fork_and_bind_sockets(struct passwd *ent_pw)
// Obtain DNS port from dnsmasq daemon
config.dns_port = daemon->port;

char *ptrname = NULL;
// Obtain PTR record used for Pi-hole PTR injection (if enabled)
if(config.pihole_ptr != PTR_NONE)
{
// Add PTR record for pi.hole, the address will be injected later
pihole_ptr = calloc(1, sizeof(struct ptr_record));
pihole_ptr->name = strdup("x.x.x.x.in-addr.arpa");
pihole_ptr->ptr = (char*)"";
pihole_ptr->next = NULL;
// Add our PTR record to the end of the linked list
if(daemon->ptr != NULL)
{
// Interate to the last PTR entry in dnsmasq's structure
struct ptr_record *ptr;
for(ptr = daemon->ptr; ptr && ptr->next; ptr = ptr->next);

// Add our record after the last existing ptr-record
ptr->next = pihole_ptr;
}
else
{
// Ours is the only record for daemon->ptr
daemon->ptr = pihole_ptr;
}
}
}

static char *get_ptrname(struct in_addr *addr)
{
static char *ptrname = NULL;
// Determine name that should be replied to with on Pi-hole PTRs
switch (config.pihole_ptr)
{
Expand All @@ -2781,13 +2827,28 @@ void FTL_fork_and_bind_sockets(struct passwd *ent_pw)

case PTR_HOSTNAMEFQDN:
{
char *suffix = daemon->domain_suffix;
char *suffix;
size_t ptrnamesize = 0;
// get_domain() will also check conditional domains configured like
// domain=<domain>[,<address range>[,local]]
if(addr)
suffix = get_domain(*addr);
else
suffix = daemon->domain_suffix;
// If local suffix is not available, we substitute "no_fqdn_available"
// see the comment about PIHOLE_PTR=HOSTNAMEFQDN in the Pi-hole docs
// for further details on why this was chosen
if(!suffix)
suffix = (char*)"no_fqdn_available";
ptrname = calloc(strlen(hostname()) + strlen(suffix) + 2, sizeof(char));

// Get enough space for domain building
size_t needspace = strlen(hostname()) + strlen(suffix) + 2;
if(ptrnamesize < needspace)
{
ptrname = realloc(ptrname, needspace);
ptrnamesize = needspace;
}

if(ptrname)
{
// Build "<hostname>.<local suffix>" domain
Expand All @@ -2800,34 +2861,11 @@ void FTL_fork_and_bind_sockets(struct passwd *ent_pw)
// Fallback to "<hostname>" on memory error
ptrname = (char*)hostname();
}
}
break;
}

// Obtain PTR record used for Pi-hole PTR injection (if enabled)
if(config.pihole_ptr != PTR_NONE)
{
// Add PTR record for pi.hole, the address will be injected later
pihole_ptr = calloc(1, sizeof(struct ptr_record));
pihole_ptr->name = strdup("x.x.x.x.in-addr.arpa");
pihole_ptr->ptr = ptrname;
pihole_ptr->next = NULL;
// Add our PTR record to the end of the linked list
if(daemon->ptr != NULL)
{
// Interate to the last PTR entry in dnsmasq's structure
struct ptr_record *ptr;
for(ptr = daemon->ptr; ptr && ptr->next; ptr = ptr->next);

// Add our record after the last existing ptr-record
ptr->next = pihole_ptr;
}
else
{
// Ours is the only record for daemon->ptr
daemon->ptr = pihole_ptr;
}
}

return ptrname;
}

// int cache_inserted, cache_live_freed are defined in dnsmasq/cache.c
Expand Down