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Correctly handle DNS server connection failures

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This commit is contained in:
dmiller
2025-05-23 17:13:06 +00:00
parent 229cb7644c
commit a55708ba5e
1 changed files with 42 additions and 9 deletions
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51
nmap_dns.cc
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@@ -208,11 +208,16 @@ struct request;
typedef struct sockaddr_storage sockaddr_storage;
struct dns_server {
enum status_t {
DISCONNECTED,
CONNECTING,
CONNECTED
};
std::string hostname;
sockaddr_storage addr;
size_t addr_len;
nsock_iod nsd;
int connected;
status_t status;
int reqs_on_wire;
int capacity;
int ssthresh;
@@ -220,7 +225,7 @@ struct dns_server {
std::list<request *> to_process;
std::list<request *> in_process;
struct timeval last_increase;
dns_server() : hostname(), addr_len(0), connected(0), reqs_on_wire(0),
dns_server() : hostname(), addr_len(0), status(DISCONNECTED), reqs_on_wire(0),
capacity(CAPACITY_MIN), ssthresh((CAPACITY_MAX + CAPACITY_MIN)/2), write_busy(0), to_process(), in_process()
{
memset(&addr, 0, sizeof(addr));
@@ -437,9 +442,9 @@ static void close_dns_servers() {
std::list<dns_server>::iterator serverI;
for(serverI = servs.begin(); serverI != servs.end(); serverI++) {
if (serverI->connected) {
if (serverI->status != dns_server::status_t::DISCONNECTED) {
nsock_iod_delete(serverI->nsd, NSOCK_PENDING_SILENT);
serverI->connected = 0;
serverI->status = dns_server::status_t::DISCONNECTED;
serverI->to_process.clear();
serverI->in_process.clear();
}
@@ -451,8 +456,19 @@ static void close_dns_servers() {
static void do_possible_writes() {
std::list<dns_server>::iterator servI;
request *tpreq;
bool all_servs_disconnected = true;
for(servI = servs.begin(); servI != servs.end(); servI++) {
switch (servI->status) {
case dns_server::status_t::CONNECTED:
all_servs_disconnected = false;
break;
case dns_server::status_t::CONNECTING:
all_servs_disconnected = false;
case dns_server::status_t::DISCONNECTED:
continue;
break;
}
if (servI->write_busy == 0 && servI->reqs_on_wire < servI->capacity) {
tpreq = NULL;
if (!new_reqs.empty()) {
@@ -473,6 +489,9 @@ static void do_possible_writes() {
}
}
}
if (all_servs_disconnected) {
nsock_loop_quit(dnspool);
}
}
// nsock write handler
@@ -897,7 +916,21 @@ static void read_evt_handler(nsock_pool nsp, nsock_event evt, void *) {
// nsock connect handler - Empty because it doesn't really need to do anything...
static void connect_evt_handler(nsock_pool, nsock_event, void *) {}
static void connect_evt_handler(nsock_pool nsp, nsock_event evt, void *srv_v) {
dns_server *srv = (dns_server *)srv_v;
assert(nse_type(evt) == NSE_TYPE_CONNECT);
if (nse_status(evt) != NSE_STATUS_SUCCESS) {
if (o.debugging) {
log_write(LOG_STDOUT, "mass_dns: connection to %s failed: %s\n",
srv->hostname.c_str(),
nse_status2str(nse_status(evt)));
}
srv->status = dns_server::status_t::DISCONNECTED;
return;
}
nsock_read(nsp, srv->nsd, read_evt_handler, -1, NULL);
srv->status = dns_server::status_t::CONNECTED;
}
// Adds DNS servers to the dns_server list. They can be separated by
@@ -950,9 +983,8 @@ static void connect_dns_servers() {
if (o.ipoptionslen)
nsock_iod_set_ipoptions(serverI->nsd, o.ipoptions, o.ipoptionslen);
nsock_connect_udp(dnspool, serverI->nsd, connect_evt_handler, NULL, (struct sockaddr *) &serverI->addr, serverI->addr_len, 53);
nsock_read(dnspool, serverI->nsd, read_evt_handler, -1, NULL);
serverI->connected = 1;
serverI->status = dns_server::status_t::CONNECTING;
nsock_connect_udp(dnspool, serverI->nsd, connect_evt_handler, &*serverI, (struct sockaddr *) &serverI->addr, serverI->addr_len, 53);
}
}
@@ -1359,7 +1391,8 @@ static void nmap_mass_dns_core(DNS::Request *requests, int num_requests) {
stat_actual = total_reqs;
int since_last = 0;
while (total_reqs > 0) {
nsock_loopstatus status = nsock_loop(dnspool, 0);
while (status == NSOCK_LOOP_TIMEOUT && total_reqs > 0) {
since_last += timeout;
if (since_last > MIN_DNS_TIMEOUT) {
since_last = 0;