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feat: implement graceful shutdown for all tarpit servers #14

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e20cd4f
feat: implement graceful shutdown for all tarpit servers
vinayaktyagi10 Mar 21, 2026
61d9885
chore: add .gitignore for build artifacts
vinayaktyagi10 Mar 21, 2026
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2 changes: 2 additions & 0 deletions .gitignore
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
bin/
output.log
63 changes: 47 additions & 16 deletions servers/coap_pit.c
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Expand Up @@ -25,6 +25,13 @@
#define MAX_BUF_LEN 1024
#define SERVER_ID "CoAP"

static volatile sig_atomic_t keepRunning = 1;

void handleSignal(int sig) {
(void)sig;
keepRunning = 0;
}

struct coapClient *clients = NULL;

int port = 5683;
Expand Down Expand Up @@ -59,7 +66,7 @@ int sendCoapBlockResponse(uint16_t messageId, uint8_t* token, uint8_t tkl, uint3
uint32_t block_opt_value = (*blockNumber << 4) | (0b1 << 3) | 0x02;
uint8_t block_len = (block_opt_value <= 0xFF) ? 1 :
(block_opt_value <= 0xFFFF) ? 2 : 3;

int payloadLength = 5;
int responseLength = 4 // base CoAP header
+ tkl // token length
Expand All @@ -69,7 +76,7 @@ int sendCoapBlockResponse(uint16_t messageId, uint8_t* token, uint8_t tkl, uint3
+ 1 // payload marker
+ payloadLength; // actual payload
char response[responseLength];

// Version (1) | Type (CON) | TKL
response[0] = (0b01 << 6) | (0b0 << 4) | (tkl & 0b1111);;
// class (2) | detail (5). Content response
Expand Down Expand Up @@ -122,6 +129,8 @@ int sendPing(uint16_t messageId, struct sockaddr_in* addr, socklen_t addrLen) {
int main(int argc, char* argv[]) {
setbuf(stdout, NULL);

int timeout = 1000;

// testing
// char msg[256];
// snprintf(msg, sizeof(msg), "%s connect %s\n",
Expand Down Expand Up @@ -172,14 +181,23 @@ int main(int argc, char* argv[]) {
pollFd.fd = sockFd;
pollFd.events = POLLIN;

while (1) {
struct sigaction sa;
sa.sa_handler = handleSignal;
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sigaction(SIGINT, &sa, NULL);
sigaction(SIGTERM, &sa, NULL);
signal(SIGPIPE, SIG_IGN);

while (keepRunning) {
long long now = currentTimeMs();
timeout = 1000;

while (clientQueueCoap.size > 0) {
if(clientQueueCoap.heapArray[0]->sendNext <= now){
struct baseClient *bc = heap_pop(&clientQueueCoap);
struct coapClient *c = (struct coapClient *)bc;

// Handle retransmits
if(!c->receivedAck || !c->receivedRst) {
if(c->retransmits < MAX_RETRANSMIT) {
Expand Down Expand Up @@ -212,17 +230,17 @@ int main(int argc, char* argv[]) {
deleteClient(c);
continue;
}
}
}

if (c->receivedGet) {
sendCoapBlockResponse(c->messageId, c->token, c->tkl, &c->blockNumber, &c->clientAddr, c->addrLen);
c->blockNumber += 1;
c->receivedAck = false;
} else if (c->receivedRst) {
sendPing(c->messageId, &c->clientAddr, c->addrLen);
c->receivedRst = false;
}
}

c->base.timeConnected += delay;
c->messageId += 1;
c->base.sendNext = now + delay;
Expand All @@ -236,6 +254,7 @@ int main(int argc, char* argv[]) {
int pollResult = poll(&pollFd, 1, timeout);
now = currentTimeMs();
if (pollResult < 0) {
if (errno == EINTR) continue;
fprintf(stderr, "Poll error with error %s", strerror(errno));
continue;
}
Expand Down Expand Up @@ -269,7 +288,7 @@ int main(int argc, char* argv[]) {
printf(" TKL : %u\n", tkl);
printf(" Code : 0x%02X (Class: %u, Detail: %u)\n", code, class, detail);
printf(" Msg ID : %u\n", msgId);

// Token (if any)
printf(" Token : ");
for (int i = 0; i < tkl; i++) {
Expand All @@ -284,7 +303,7 @@ int main(int argc, char* argv[]) {
// Malformed request. Send 4.00 Bad Request
uint8_t response[4];
uint8_t resp_type = (type == TYPE_CONFIRMABLE) ? TYPE_ACK : TYPE_NON_CONFIRMABLE;

response[0] = (0b01 << 6) | (resp_type << 4) | 0; // Ver=1, Type=ACK/NON, TKL=0
response[1] = (0b100 << 5) | 0b0; // Code 4.00 (Bad Request)
response[2] = msgId >> 8;
Expand All @@ -293,7 +312,7 @@ int main(int argc, char* argv[]) {

sendto(sockFd, response, resp_len, 0, (struct sockaddr *)&clientAddr, addrLen);
continue;
}
}
else if (version != 1){
// Must be silently ignored
continue;
Expand All @@ -302,7 +321,7 @@ int main(int argc, char* argv[]) {
}

// TODO: Ignore extended methods (send "method not allowed" response)
// TODO: Handle requests while the client is still receiving blocks.
// TODO: Handle requests while the client is still receiving blocks.
struct coapClient* client = findExistingClient(&clientAddr);
if(client == NULL) {
client = malloc(sizeof(struct coapClient));
Expand Down Expand Up @@ -332,7 +351,7 @@ int main(int argc, char* argv[]) {
printf("%s", msg);
sendMetric(msg);
}

if (type == TYPE_RST) {
client->receivedRst = true;
}
Expand All @@ -343,9 +362,9 @@ int main(int argc, char* argv[]) {
else if (class == CLASS_REQUEST && detail == DETAIL_GET) {
printf("GET request from %s of type %d with tkl=%d and msgId1=%u\n", inet_ntoa(clientAddr.sin_addr), type, tkl, msgId);
client->receivedGet = true;
}
}

// If a CON (Confirmable) request, first send seperate ACK response.
// If a CON (Confirmable) request, first send seperate ACK response.
// The response does not need to be confirmable. (5.2.2 and 5.2.3)
if (type == TYPE_CONFIRMABLE) {
uint8_t ack[4];
Expand All @@ -359,7 +378,19 @@ int main(int argc, char* argv[]) {
}
}
}
printf("Shutting down CoAP server gracefully\n");
while (clientQueueCoap.size > 0) {
struct baseClient *bc = heap_pop(&clientQueueCoap);
struct coapClient *c = (struct coapClient *)bc;
char msg[256];
snprintf(msg, sizeof(msg), "%s disconnect %s %lld\n",
SERVER_ID, c->base.ipaddr, c->base.timeConnected);
printf("%s", msg);
sendMetric(msg);
deleteClient(c);
}

close(sockFd);
printf("CoAP server shut down successfully\n");
return 0;
}
}
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