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Add UDP discovery and heartbeat-miss notices to remchild

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This commit is contained in:
Fisto
2026-09-22 19:31:19 +02:00
parent a7ab2a22f7
commit e38d7d07a2
4 changed files with 278 additions and 22 deletions
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remchild/client/main.c
+154 -16
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@@ -31,6 +31,10 @@
#include "words.h"
#define DISCOVERY_PORT 8798
#define DISCOVERY_WINDOW_MS 5000
#define DISCOVERY_MAX 8
#define HEARTBEAT_FAST_MS 10000
#define HEARTBEAT_MID_MS 30000
#define HEARTBEAT_SLOW_MS 300000
@@ -38,6 +42,12 @@
#define MID_UNTIL_MS 360000
#define LINE_MAX 4096
static long heartbeat_interval(long elapsed_ms) {
if (elapsed_ms < FAST_UNTIL_MS) return HEARTBEAT_FAST_MS;
if (elapsed_ms < MID_UNTIL_MS) return HEARTBEAT_MID_MS;
return HEARTBEAT_SLOW_MS;
}
static long now_ms(void) {
struct timespec ts;
clock_gettime(CLOCK_MONOTONIC, &ts);
@@ -104,6 +114,100 @@ static void name_for_id(const unsigned char *id, size_t len, char *out, size_t c
snprintf(out, cap, "%s %s", REMCHILD_FIRST[first], REMCHILD_SECOND[second]);
}
struct Discovered {
char ip[64];
char name[64];
char id[64];
int port;
};
/*
* Ask the LAN who is there. Probes go out as broadcast and to loopback; a
* server answers with its beacon, and the address comes from the reply.
* Waits up to DISCOVERY_WINDOW_MS. Returns the number of servers found.
*/
static int discover(struct Discovered *found, int cap) {
int fd = socket(AF_INET, SOCK_DGRAM, 0);
if (fd < 0) return 0;
int one = 1;
setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &one, sizeof(one));
struct sockaddr_in local = {0};
local.sin_family = AF_INET;
local.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(fd, (struct sockaddr *)&local, sizeof(local)) != 0) {
close(fd);
return 0;
}
struct sockaddr_in broadcast = {0};
broadcast.sin_family = AF_INET;
broadcast.sin_port = htons(DISCOVERY_PORT);
broadcast.sin_addr.s_addr = htonl(INADDR_BROADCAST);
struct sockaddr_in loopback = broadcast;
loopback.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
const char *probe = "{\"type\":\"veskslop-remchild-probe\",\"version\":\"0.1\"}";
long deadline = now_ms() + DISCOVERY_WINDOW_MS;
long next_probe = 0;
int count = 0;
while (now_ms() < deadline) {
if (now_ms() >= next_probe) {
sendto(fd, probe, strlen(probe), 0, (struct sockaddr *)&broadcast, sizeof(broadcast));
sendto(fd, probe, strlen(probe), 0, (struct sockaddr *)&loopback, sizeof(loopback));
next_probe = now_ms() + 1000;
}
struct pollfd pfd = {fd, POLLIN, 0};
if (poll(&pfd, 1, 200) <= 0) continue;
if (!(pfd.revents & POLLIN)) continue;
char buffer[1024];
struct sockaddr_in from;
socklen_t from_len = sizeof(from);
ssize_t got = recvfrom(fd, buffer, sizeof(buffer) - 1, 0, (struct sockaddr *)&from, &from_len);
if (got <= 0) continue;
buffer[got] = 0;
if (!strstr(buffer, "veskslop-remchild") || strstr(buffer, "probe")) continue;
char ip[64];
if (!inet_ntop(AF_INET, &from.sin_addr, ip, sizeof(ip))) continue;
int port = 0;
char name[64] = "veskslop";
char id[64] = "";
char *match = strstr(buffer, "\"port\":");
if (match) port = atoi(match + 7);
match = strstr(buffer, "\"name\":\"");
if (match) sscanf(match + 8, "%63[^\"]", name);
match = strstr(buffer, "\"id\":\"");
if (match) sscanf(match + 6, "%63[^\"]", id);
if (port <= 0) continue;
// One server can answer from both loopback and its LAN address; the
// beacon id identifies it.
int duplicate = 0;
for (int i = 0; i < count; i++) {
if (id[0] && found[i].id[0] && !strcmp(found[i].id, id)) duplicate = 1;
else if (!id[0] && !found[i].id[0] && !strcmp(found[i].name, name) && found[i].port == port) duplicate = 1;
}
if (duplicate || count >= cap) continue;
snprintf(found[count].ip, sizeof(found[count].ip), "%s", ip);
snprintf(found[count].name, sizeof(found[count].name), "%s", name);
snprintf(found[count].id, sizeof(found[count].id), "%s", id);
found[count].port = port;
count++;
}
close(fd);
return count;
}
static int connect_to(const char *host, int port) {
struct sockaddr_in addr = {0};
addr.sin_family = AF_INET;
@@ -159,17 +263,43 @@ int main(int argc, char **argv) {
int interactive = isatty(STDIN_FILENO);
if (!host[0]) {
printf("Server address (host:port): ");
struct Discovered found[DISCOVERY_MAX];
printf("[remchild] looking for a server on the LAN for %d seconds...\n", DISCOVERY_WINDOW_MS / 1000);
fflush(stdout);
char line[128];
if (!fgets(line, sizeof(line), stdin)) return 1;
line[strcspn(line, "\n")] = 0;
char *colon = strrchr(line, ':');
if (colon) {
*colon = 0;
port = atoi(colon + 1);
int count = discover(found, DISCOVERY_MAX);
if (count == 1) {
printf("[remchild] found %s at %s:%d\n", found[0].name, found[0].ip, found[0].port);
snprintf(host, sizeof(host), "%s", found[0].ip);
port = found[0].port;
} else if (count > 1) {
printf("[remchild] found %d servers:\n", count);
for (int i = 0; i < count; i++) {
printf(" %d) %s at %s:%d\n", i + 1, found[i].name, found[i].ip, found[i].port);
}
printf("pick one [1]: ");
fflush(stdout);
char pick_line[32];
int pick = 1;
if (fgets(pick_line, sizeof(pick_line), stdin)) pick = atoi(pick_line);
if (pick < 1 || pick > count) pick = 1;
printf("[remchild] using %s at %s:%d\n", found[pick - 1].name, found[pick - 1].ip, found[pick - 1].port);
snprintf(host, sizeof(host), "%s", found[pick - 1].ip);
port = found[pick - 1].port;
} else {
printf("[remchild] no server answered discovery.\n");
printf("Server address (host:port): ");
fflush(stdout);
char line[128];
if (!fgets(line, sizeof(line), stdin)) return 1;
line[strcspn(line, "\n")] = 0;
char *colon = strrchr(line, ':');
if (colon) {
*colon = 0;
port = atoi(colon + 1);
}
snprintf(host, sizeof(host), "%s", line);
}
snprintf(host, sizeof(host), "%s", line);
}
unsigned char id[32];
@@ -196,6 +326,7 @@ int main(int argc, char **argv) {
printf("[remchild] identity %s (name: %s)\n", id_len == 6 ? "MAC" : "machine-id", name);
printf("[remchild] connecting to %s:%d\n", host, port);
fflush(stdout);
int fd = connect_to(host, port);
if (fd < 0) {
@@ -214,8 +345,9 @@ int main(int argc, char **argv) {
char hello[512];
snprintf(hello, sizeof(hello),
"{\"type\":\"hello\",\"id\":\"%s\",\"name\":\"%s\",\"platform\":\"linux\",\"version\":\"0.1\"}",
id_hex, name);
"{\"type\":\"hello\",\"id\":\"%s\",\"name\":\"%s\",\"platform\":\"linux\","
"\"version\":\"0.1\",\"heartbeatMs\":%ld}",
id_hex, name, heartbeat_interval(0));
send_line(fd, hello);
long started = now_ms();
@@ -234,13 +366,12 @@ int main(int argc, char **argv) {
for (;;) {
long now = now_ms();
long interval = now - started < FAST_UNTIL_MS ? HEARTBEAT_FAST_MS
: now - started < MID_UNTIL_MS ? HEARTBEAT_MID_MS
: HEARTBEAT_SLOW_MS;
long interval = heartbeat_interval(now - started);
if (now - last_beat >= interval) {
char beat[128];
snprintf(beat, sizeof(beat), "{\"type\":\"heartbeat\",\"ts\":%ld}", (long)time(NULL));
snprintf(beat, sizeof(beat), "{\"type\":\"heartbeat\",\"ts\":%ld,\"heartbeatMs\":%ld}",
(long)time(NULL), interval);
send_line(fd, beat);
last_beat = now;
}
@@ -272,9 +403,16 @@ int main(int argc, char **argv) {
} else if (strstr(line, "\"type\":\"pong\"")) {
if (ping_sent_at) printf("[remchild] pong seq=%d rtt=%ldms\n", ping_seq, now_ms() - ping_sent_at);
answered_ping = 1;
} else if (strstr(line, "\"type\":\"notice\"")) {
int missed = 0;
char *value = strstr(line, "\"missed\":");
if (value) missed = atoi(value + 9);
printf("[remchild] notice: the server missed %d heartbeat(s); the connection may be unstable.\n",
missed);
} else if (strstr(line, "\"type\":\"ping\"")) {
int seq = 0;
sscanf(line, "%*[^\"]\"seq\":%d", &seq);
char *value = strstr(line, "\"seq\":");
if (value) seq = atoi(value + 6);
char pong[64];
snprintf(pong, sizeof(pong), "{\"type\":\"pong\",\"seq\":%d}", seq);
send_line(fd, pong);