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#include "rcon.h"
#include "../log.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/time.h>
/* ── Packet structure ────────────────────────────────────────────────────── */
/*
* On the wire, each RCON packet is:
* [int32 size] [int32 id] [int32 type] [string\0] [\0]
*
* 'size' = sizeof(id) + sizeof(type) + strlen(body) + 2
* = 4 + 4 + strlen(body) + 2
*
* We use a fixed-size buffer — RCON responses for console commands are
* generally small (< 4KB), but we handle multi-packet responses.
*/
#define RCON_BUF_SIZE 4096
#define RCON_HDR_SIZE 12 /* size(4) + id(4) + type(4) */
#define RCON_TIMEOUT_S 5
typedef struct {
int32_t size;
int32_t id;
int32_t type;
char body[RCON_BUF_SIZE];
} RconPacket;
/* ── Low-level helpers ───────────────────────────────────────────────────── */
static int tcp_connect(const char *host, int port) {
struct addrinfo hints, *res, *rp;
char port_str[8];
int fd = -1;
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
snprintf(port_str, sizeof(port_str), "%d", port);
if (getaddrinfo(host, port_str, &hints, &res) != 0) {
log_error("rcon: getaddrinfo(%s): %s", host, strerror(errno));
return -1;
}
for (rp = res; rp; rp = rp->ai_next) {
fd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
if (fd < 0) continue;
/* Set connect timeout */
struct timeval tv = { .tv_sec = RCON_TIMEOUT_S, .tv_usec = 0 };
setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv));
if (connect(fd, rp->ai_addr, rp->ai_addrlen) == 0)
break;
close(fd);
fd = -1;
}
freeaddrinfo(res);
if (fd < 0)
log_error("rcon: could not connect to %s:%d", host, port);
return fd;
}
static int rcon_send(int fd, int32_t id, int32_t type, const char *body) {
int body_len = body ? (int)strlen(body) : 0;
int32_t size = 4 + 4 + body_len + 2; /* id + type + body + two nulls */
/* Build packet in a local buffer */
uint8_t buf[RCON_BUF_SIZE + RCON_HDR_SIZE];
int32_t le_size = htole32(size);
int32_t le_id = htole32(id);
int32_t le_type = htole32(type);
memcpy(buf, &le_size, 4);
memcpy(buf + 4, &le_id, 4);
memcpy(buf + 8, &le_type, 4);
if (body_len > 0)
memcpy(buf + 12, body, body_len);
buf[12 + body_len] = '\0';
buf[12 + body_len + 1] = '\0';
int total = 4 + size;
ssize_t n = write(fd, buf, total);
return (n == total) ? 0 : -1;
}
static int rcon_recv(int fd, RconPacket *pkt) {
uint8_t hdr[12];
ssize_t n;
/* Read the fixed 12-byte header */
int got = 0;
while (got < 12) {
n = read(fd, hdr + got, 12 - got);
if (n <= 0) return -1;
got += n;
}
int32_t size, id, type;
memcpy(&size, hdr, 4); size = le32toh(size);
memcpy(&id, hdr + 4, 4); id = le32toh(id);
memcpy(&type, hdr + 8, 4); type = le32toh(type);
pkt->size = size;
pkt->id = id;
pkt->type = type;
/* Body length = size - sizeof(id) - sizeof(type) - 2 trailing nulls */
int body_len = size - 4 - 4 - 2;
if (body_len < 0 || body_len >= RCON_BUF_SIZE)
return -1;
if (body_len > 0) {
got = 0;
while (got < body_len) {
n = read(fd, pkt->body + got, body_len - got);
if (n <= 0) return -1;
got += n;
}
}
pkt->body[body_len] = '\0';
/* Consume the two trailing null bytes */
uint8_t nulls[2];
(void)read(fd, nulls, 2);
return 0;
}
/* ── Public interface ────────────────────────────────────────────────────── */
int rcon_exec(const char *host, int port, const char *password,
const char *command, char *response, int resp_len) {
int fd = tcp_connect(host, port);
if (fd < 0) return -1;
RconPacket pkt;
int auth_id = 1;
int exec_id = 2;
/* Step 1: Send auth request */
if (rcon_send(fd, auth_id, RCON_AUTH_REQUEST, password) != 0) {
log_error("rcon: send auth failed");
close(fd);
return -1;
}
/*
* Step 2: Read auth response.
*
* srcds sends packets in this order after an auth request:
* 1. SERVERDATA_RESPONSE_VALUE (type=0, id=auth_id) -- empty body
* 2. SERVERDATA_AUTH_RESPONSE (type=2, id=auth_id) -- success
* OR
* SERVERDATA_AUTH_RESPONSE (type=2, id=-1) -- bad password
*
* Loop ignoring type=0 packets until we see type=2.
* 8 attempts handles servers that send extra interleaved packets.
*/
int authed = 0;
for (int attempt = 0; attempt < 8; attempt++) {
if (rcon_recv(fd, &pkt) != 0) {
log_error("rcon: recv auth response failed (attempt %d)", attempt);
close(fd);
return -1;
}
log_debug("rcon: auth packet type=%d id=%d", pkt.type, pkt.id);
if (pkt.type == 2) {
if (pkt.id == -1) {
log_error("rcon: bad password -- verify rcon_password in "
"server.cfg matches the unit file configuration");
close(fd);
return -1;
}
authed = 1;
break;
}
/* type=0: empty value packet, keep reading */
}
if (!authed) {
log_error("rcon: no auth response after 8 packets");
close(fd);
return -1;
}
/* Step 3: Send command */
if (rcon_send(fd, exec_id, RCON_EXEC_REQUEST, command) != 0) {
log_error("rcon: send command failed");
close(fd);
return -1;
}
/*
* Step 4: Read response.
* Large responses may be split across multiple packets.
* We send a known "terminator" packet and collect until we see its id.
* This is the standard trick for handling multi-packet responses.
*/
int term_id = 3;
rcon_send(fd, term_id, RCON_EXEC_REQUEST, "");
int pos = 0;
if (response) response[0] = '\0';
for (int i = 0; i < 64; i++) { /* safety limit */
if (rcon_recv(fd, &pkt) != 0) break;
if (pkt.id == term_id)
break; /* saw our terminator response — done */
if (response && pkt.body[0]) {
int chunk = (int)strlen(pkt.body);
if (pos + chunk < resp_len - 1) {
memcpy(response + pos, pkt.body, chunk);
pos += chunk;
response[pos] = '\0';
}
}
}
close(fd);
return 0;
}
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