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NTP: add ability to configure multiple servers
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With this change, it is possible to configure the NTP klib with
multiple NTP servers, by inserting an `ntp_servers` array in the
root tuple of the manifest, where each array element follows the
syntax '<addr>[:<port]'; <addr> can be an IP address or a fully
qualified domain name; if the optional <port> is not present, the
default NTP port 123 is used.
Example configuration with 2 servers:
`ntp_servers:[us.pool.ntp.org 12.34.56.78:1234]`
When multiple servers are configured, the NTP klib starts by using
the first server, and switches to the next server (in a round robin
fashion) if no valid response is received from the current server.
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@francescolavra
francescolavra committed Jul 13, 2022
1 parent 6565416 commit 7cdb1d3
Showing 1 changed file with 76 additions and 22 deletions.
98 changes: 76 additions & 22 deletions klib/ntp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,11 @@ struct ntp_sample {
u64 peer_dispersion;
};

typedef struct ntp_server {
char *addr;
u16 port;
} *ntp_server;

declare_closure_struct(0, 2, void, ntp_query_func,
u64, expiry, u64, overruns);
declare_closure_struct(0, 2, void, ntp_slew_complete_func,
Expand All @@ -79,8 +84,8 @@ declare_closure_struct(0, 2, void, ntp_raw_update_func,
u64, expiry, u64, overruns);

static struct {
char server_addr[256];
u16 server_port;
vector servers;
int current_server;
struct udp_pcb *pcb;
struct timer query_timer;
struct timer slew_timer;
Expand Down Expand Up @@ -161,6 +166,10 @@ static void ntp_query_complete(boolean success)
{
if (success) {
ntp.query_errors = 0;
} else if ((ntp.nsamples == 0) && (vector_length(ntp.servers) > 1)) {
if (++ntp.current_server == vector_length(ntp.servers))
ntp.current_server = 0;
ntp_debug("switching to server %d\n", ntp.current_server);
} else if ((++ntp.query_errors > NTP_QUERY_ATTEMPTS) &&
(ntp.query_interval < ntp.pollmax)) {
ntp.query_interval++;
Expand Down Expand Up @@ -299,7 +308,8 @@ static void ntp_query(const ip_addr_t *server_addr, boolean lwip_locked)
runtime_memcpy(&ntp.last_originate_time, &t, sizeof(t));
if (!lwip_locked)
lwip_lock();
err_t err = udp_sendto(ntp.pcb, p, server_addr, ntp.server_port);
ntp_server server = vector_get(ntp.servers, ntp.current_server);
err_t err = udp_sendto(ntp.pcb, p, server_addr, server->port);
if (err != ERR_OK) {
rprintf("%s: failed to send request: %d\n", __func__, err);
ntp_query_complete(false);
Expand Down Expand Up @@ -669,7 +679,8 @@ define_closure_function(0, 2, void, ntp_query_func,
}
ip_addr_t server_addr;
lwip_lock();
err_t err = dns_gethostbyname(ntp.server_addr, &server_addr, ntp_dns_cb, 0);
ntp_server server = vector_get(ntp.servers, ntp.current_server);
err_t err = dns_gethostbyname(server->addr, &server_addr, ntp_dns_cb, 0);
lwip_unlock();
if (err == ERR_OK)
ntp_query(&server_addr, false);
Expand All @@ -690,35 +701,78 @@ define_closure_function(0, 2, void, ntp_raw_update_func,
(timer_handler)&ntp.raw_update_func);
}

static void ntp_server_add(heap h, buffer addr, u16 port)
{
ntp_debug("adding server %b (port %d)\n", addr, port);
ntp_server server = allocate(h, sizeof(*server));
assert(server != INVALID_ADDRESS);
bytes addr_len = buffer_length(addr);
server->addr = allocate(h, addr_len + 1);
assert(server->addr != INVALID_ADDRESS);
runtime_memcpy(server->addr, buffer_ref(addr, 0), addr_len);
server->addr[addr_len] = '\0';
server->port = port;
vector_push(ntp.servers, server);
}

static boolean ntp_server_parse(heap h, buffer server)
{
int separator = buffer_strchr(server, ':');
if ((separator == 0) || (separator == buffer_length(server) - 1))
return false;
buffer addr;
u16 port;
if (separator > 0) {
buffer port_buf = alloca_wrap_buffer(buffer_ref(server, separator + 1),
buffer_length(server) - separator - 1);
u64 val;
if (!u64_from_value(port_buf, &val) || (val > U16_MAX))
return false;
addr = alloca_wrap_buffer(buffer_ref(server, 0), separator);
port = val;
} else {
addr = server;
port = NTP_PORT_DEFAULT;
}
ntp_server_add(h, addr, port);
return true;
}

int init(status_handler complete)
{
tuple root = get_root_tuple();
if (!root) {
rprintf("NTP: failed to get root tuple\n");
return KLIB_INIT_FAILED;
}
buffer server_addr = get(root, sym_intern(ntp_address, intern));
if (server_addr) {
bytes len = buffer_length(server_addr);
if (len >= sizeof(ntp.server_addr)) {
rprintf("NTP: invalid server address\n");
return KLIB_INIT_FAILED;
heap h = heap_locked(get_kernel_heaps());
tuple servers = get_tuple(root, sym(ntp_servers));
int server_count;
if (servers) {
server_count = tuple_count(servers);
if (server_count == 0) {
servers = 0;
server_count = 1;
}
runtime_memcpy(ntp.server_addr, buffer_ref(server_addr, 0), len);
ntp.server_addr[len] = '\0';
} else {
runtime_memcpy(ntp.server_addr, NTP_SERVER_DEFAULT, sizeof(NTP_SERVER_DEFAULT));
}
value server_port = get(root, sym_intern(ntp_port, intern));
if (server_port) {
u64 port;
if (!u64_from_value(server_port, &port) || (port > U16_MAX)) {
rprintf("NTP: invalid server port\n");
} else {
server_count = 1;
}
ntp.servers = allocate_vector(h, server_count);
assert(ntp.servers != INVALID_ADDRESS);
if (servers) {
string server;
for (int i = 0; (server = get_string(servers, intern_u64(i))); i++) {
if (!ntp_server_parse(h, server)) {
rprintf("NTP: invalid server '%b'\n", server);
return KLIB_INIT_FAILED;
}
}
if (vector_length(ntp.servers) == 0) {
rprintf("NTP: invalid servers %v\n", servers);
return KLIB_INIT_FAILED;
}
ntp.server_port = port;
} else {
ntp.server_port = NTP_PORT_DEFAULT;
ntp_server_add(h, alloca_wrap_cstring(NTP_SERVER_DEFAULT), NTP_PORT_DEFAULT);
}
ntp.pollmin = 4;
ntp.pollmax = 10;
Expand Down

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