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tls: yield downstream read retries to the event loop [Backport to 5.0] #12141

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tls: yield downstream read retries to the event loop [Backport to 5.0] #12141

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52dc27c
tls: yield downstream reads to event loop
edsiper Jul 22, 2026
dc675fa
in_forward: retain retryable TLS connections
edsiper Jul 22, 2026
86a2f07
in_http: retain retryable TLS connections
edsiper Jul 22, 2026
9ef9b18
in_mqtt: retain retryable TLS connections
edsiper Jul 22, 2026
854f656
in_syslog: retain retryable TLS connections
edsiper Jul 22, 2026
f30e3a3
in_tcp: retain retryable TLS connections
edsiper Jul 22, 2026
a4e27cb
in_unix_socket: retain retryable TLS connections
edsiper Jul 22, 2026
1e2a2a4
http_server: retain retryable TLS connections
edsiper Jul 22, 2026
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9 changes: 9 additions & 0 deletions include/fluent-bit/flb_io.h
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,15 @@
/* Other features */
#define FLB_IO_IPV6 32 /* network I/O uses IPv6 */

/* Retryable network I/O results */
#define FLB_IO_WANT_READ -0x7e4
#define FLB_IO_WANT_WRITE -0x7e6

static inline int flb_io_net_is_retry(ssize_t result)
{
return result == FLB_IO_WANT_READ || result == FLB_IO_WANT_WRITE;
}

struct flb_connection;

int flb_io_net_accept(struct flb_connection *connection,
Expand Down
5 changes: 3 additions & 2 deletions include/fluent-bit/tls/flb_tls.h
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Original file line number Diff line number Diff line change
Expand Up @@ -25,15 +25,16 @@
#include <fluent-bit/flb_info.h>
#include <fluent-bit/flb_config.h>
#include <fluent-bit/flb_coro.h>
#include <fluent-bit/flb_io.h>
#include <stddef.h>

#define FLB_TLS_ALPN_MAX_LENGTH 16

#define FLB_TLS_CLIENT "Fluent Bit"

/* TLS backend return status on read/write */
#define FLB_TLS_WANT_READ -0x7e4
#define FLB_TLS_WANT_WRITE -0x7e6
#define FLB_TLS_WANT_READ FLB_IO_WANT_READ
#define FLB_TLS_WANT_WRITE FLB_IO_WANT_WRITE

/* Cert Flags */
#define FLB_TLS_CA_ROOT 1
Expand Down
8 changes: 8 additions & 0 deletions plugins/in_forward/fw_conn.c
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,10 @@ static int fw_conn_event_internal(struct flb_connection *connection)
flb_plg_trace(ctx->ins, "handshake status = %d", conn->handshake_status);

ret = fw_prot_secure_forward_handshake(ctx->ins, conn);
if (flb_io_net_is_retry(ret)) {
return 0;
}

if (ret == -1) {
flb_plg_trace(ctx->ins, "fd=%i closed connection", event->fd);
fw_conn_del(conn);
Expand Down Expand Up @@ -108,6 +112,10 @@ static int fw_conn_event_internal(struct flb_connection *connection)
(void *) &conn->buf[conn->buf_len],
available);

if (flb_io_net_is_retry(bytes)) {
return 0;
}

if (bytes > 0) {
read_bytes = (size_t) bytes;
flb_plg_trace(ctx->ins, "read()=%zd pre_len=%zu now_len=%zu",
Expand Down
43 changes: 31 additions & 12 deletions plugins/in_forward/fw_prot.c
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Expand Up @@ -140,45 +140,54 @@ static inline void print_msgpack_error_code(struct flb_input_instance *in,

/* Read a secure forward msgpack message for handshake */
static int secure_forward_read(struct flb_input_instance *in,
struct flb_connection *connection,
char *buf, size_t size, size_t *out_len)
struct fw_conn *conn, size_t size,
size_t *out_len)
{
int ret;
size_t off;
size_t avail;
size_t buf_off = 0;
msgpack_unpacked result;

msgpack_unpacked_init(&result);
while (1) {
avail = size - buf_off;
if (avail < 1) {
if (conn->buf_len >= size) {
goto error;
}

avail = size - conn->buf_len;

/* Read the message */
ret = flb_io_net_read(connection, buf + buf_off, size - buf_off);
ret = flb_io_net_read(conn->connection,
conn->buf + conn->buf_len, avail);
Comment on lines +160 to +161

@chatgpt-codex-connector chatgpt-codex-connector Bot Jul 23, 2026

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P1 Badge Bound secure-forward reads to the allocated buffer

When secure-forward is enabled and buffer_chunk_size is configured below 1023, conn->buf is only that configured size, but check_ping() calls this helper with size == 1023, so flb_io_net_read() can write past the end of conn->buf before msgpack validation runs. Please cap avail by conn->buf_size - conn->buf_len or grow the connection buffer before reading the PING.

Useful? React with 👍 / 👎.

if (flb_io_net_is_retry(ret)) {
msgpack_unpacked_destroy(&result);
return ret;
}

if (ret <= 0) {
flb_plg_debug(in, "read %d byte(s)", ret);
goto error;
}
buf_off += ret;
conn->buf_len += ret;

/* Validate */
off = 0;
ret = msgpack_unpack_next(&result, buf, buf_off, &off);
ret = msgpack_unpack_next(&result, conn->buf, conn->buf_len, &off);
switch (ret) {
case MSGPACK_UNPACK_SUCCESS:
msgpack_unpacked_destroy(&result);
*out_len = buf_off;
*out_len = conn->buf_len;
return 0;
case MSGPACK_UNPACK_CONTINUE:
break;
default:
print_msgpack_error_code(in, ret, "handshake");
goto error;
};
}

error:
conn->buf_len = 0;
msgpack_unpacked_destroy(&result);
return -1;
}
Expand Down Expand Up @@ -506,7 +515,6 @@ static int check_ping(struct flb_input_instance *ins,
flb_sds_t *out_shared_key_salt)
{
int ret;
char buf[1024];
size_t out_len;
size_t off;
msgpack_unpacked result;
Expand All @@ -531,7 +539,12 @@ static int check_ping(struct flb_input_instance *ins,
}

/* Wait for client PING */
ret = secure_forward_read(ins, conn->connection, buf, sizeof(buf) - 1, &out_len);
ret = secure_forward_read(ins, conn, 1023, &out_len);
if (flb_io_net_is_retry(ret)) {
flb_free(serverside);
return ret;
}

if (ret == -1) {
flb_free(serverside);
flb_plg_error(ins, "handshake error expecting PING");
Expand All @@ -541,7 +554,8 @@ static int check_ping(struct flb_input_instance *ins,
/* Unpack message and validate */
off = 0;
msgpack_unpacked_init(&result);
ret = msgpack_unpack_next(&result, buf, out_len, &off);
ret = msgpack_unpack_next(&result, conn->buf, out_len, &off);
conn->buf_len = 0;
if (ret != MSGPACK_UNPACK_SUCCESS) {
flb_free(serverside);
print_msgpack_error_code(ins, ret, "PING");
Expand Down Expand Up @@ -1206,6 +1220,11 @@ int fw_prot_secure_forward_handshake(struct flb_input_instance *ins,
reason = flb_sds_create_size(32);
flb_plg_debug(ins, "protocol: checking PING");
ping_ret = check_ping(ins, conn, &shared_key_salt);
if (flb_io_net_is_retry(ping_ret)) {
flb_sds_destroy(reason);
return ping_ret;
}

if (ping_ret == -1) {
flb_plg_error(ins, "handshake error checking PING");

Expand Down
4 changes: 4 additions & 0 deletions plugins/in_http/http_conn.c
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Expand Up @@ -107,6 +107,10 @@ static int http_conn_event(void *data)
(void *) &conn->buf_data[conn->buf_len],
available);

if (flb_io_net_is_retry(bytes)) {
return 0;
}

if (bytes <= 0) {
flb_plg_trace(ctx->ins, "fd=%i closed connection", event->fd);
http_conn_del(conn);
Expand Down
4 changes: 4 additions & 0 deletions plugins/in_mqtt/mqtt_conn.c
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Expand Up @@ -54,6 +54,10 @@ int mqtt_conn_event(void *data)
(void *) &conn->buf[conn->buf_len],
available);

if (flb_io_net_is_retry(bytes)) {
return 0;
}

if (bytes > 0) {
conn->buf_len += bytes;
flb_plg_trace(ctx->ins, "[fd=%i] read()=%i bytes",
Expand Down
4 changes: 4 additions & 0 deletions plugins/in_syslog/syslog_conn.c
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Original file line number Diff line number Diff line change
Expand Up @@ -97,6 +97,10 @@ int syslog_stream_conn_event(void *data)
(void *) &conn->buf_data[conn->buf_len],
available);

if (flb_io_net_is_retry(bytes)) {
return 0;
}

if (bytes > 0) {
flb_plg_trace(ctx->ins, "read()=%i pre_len=%zu now_len=%zu",
bytes, conn->buf_len, conn->buf_len + bytes);
Expand Down
5 changes: 5 additions & 0 deletions plugins/in_tcp/tcp_conn.c
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Original file line number Diff line number Diff line change
Expand Up @@ -452,6 +452,11 @@ int tcp_conn_event(void *data)
(void *) &conn->buf_data[conn->buf_len],
available);

if (flb_io_net_is_retry(bytes)) {
conn->busy = FLB_FALSE;
return 0;
}

if (bytes <= 0) {
flb_plg_trace(ctx->ins, "fd=%i closed connection", event->fd);
conn->busy = FLB_FALSE;
Expand Down
4 changes: 4 additions & 0 deletions plugins/in_unix_socket/unix_socket_conn.c
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Original file line number Diff line number Diff line change
Expand Up @@ -269,6 +269,10 @@ int unix_socket_conn_event(void *data)
(void *) &conn->buf_data[conn->buf_len],
available);

if (flb_io_net_is_retry(bytes)) {
return 0;
}

if (bytes <= 0) {
if (!ctx->dgram_mode_flag) {
flb_plg_trace(ctx->ins, "fd=%i closed connection", event->fd);
Expand Down
4 changes: 4 additions & 0 deletions src/http_server/flb_http_server.c
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Original file line number Diff line number Diff line change
Expand Up @@ -247,6 +247,10 @@ static int flb_http_server_session_read(struct flb_http_server_session *session)
(void *) session->read_buffer,
session->read_buffer_size);

if (flb_io_net_is_retry(result)) {
return 0;
}

if (result <= 0) {
return -1;
}
Expand Down
29 changes: 28 additions & 1 deletion src/tls/flb_tls.c
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Original file line number Diff line number Diff line change
Expand Up @@ -162,7 +162,7 @@ static inline int io_tls_event_switch(struct flb_tls_session *session,
event = &session->connection->event;
event_loop = session->connection->evl;

if ((event->mask & mask) == 0) {
if ((event->mask & (MK_EVENT_READ | MK_EVENT_WRITE)) != mask) {
ret = mk_event_add(event_loop,
event->fd,
FLB_ENGINE_EV_THREAD,
Expand Down Expand Up @@ -345,12 +345,19 @@ int flb_tls_set_client_thumbprints(struct flb_tls *tls, const char *thumbprints)

int flb_tls_net_read(struct flb_tls_session *session, void *buf, size_t len)
{
int event_driven;
time_t timeout_timestamp;
time_t current_timestamp;
struct flb_tls *tls;
int ret;

tls = session->tls;
event_driven = FLB_FALSE;

if (session->connection->type == FLB_DOWNSTREAM_CONNECTION &&
MK_EVENT_IS_REGISTERED((&session->connection->event))) {
event_driven = FLB_TRUE;
}

if (session->connection->net->io_timeout > 0) {
timeout_timestamp = time(NULL) + session->connection->net->io_timeout;
Expand All @@ -365,6 +372,14 @@ int flb_tls_net_read(struct flb_tls_session *session, void *buf, size_t len)
current_timestamp = time(NULL);

if (ret == FLB_TLS_WANT_READ) {
if (event_driven) {
if (io_tls_event_switch(session, MK_EVENT_READ) == -1) {
return -1;
}

return FLB_TLS_WANT_READ;
}

if (timeout_timestamp > 0 &&
timeout_timestamp <= current_timestamp) {
return ret;
Expand All @@ -373,6 +388,14 @@ int flb_tls_net_read(struct flb_tls_session *session, void *buf, size_t len)
goto retry_read;
}
else if (ret == FLB_TLS_WANT_WRITE) {
if (event_driven) {
if (io_tls_event_switch(session, MK_EVENT_READ | MK_EVENT_WRITE) == -1) {

@chatgpt-codex-connector chatgpt-codex-connector Bot Jul 23, 2026

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P2 Badge Preserve custom event dispatch for TLS write retries

When a downstream TLS read returns FLB_TLS_WANT_WRITE, this new path calls io_tls_event_switch(), whose mk_event_add(..., FLB_ENGINE_EV_THREAD, ...) re-registers the already-registered input/http-server connection as a thread event instead of the FLB_ENGINE_EV_CUSTOM handler it was using. In the normal downstream input registrations there is no coroutine waiting for that follow-up writable notification, so the engine consumes the event without invoking the connection handler and the TLS connection can remain stuck in the retry state; preserve the existing event type/handler when switching the mask.

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return -1;
}

return FLB_TLS_WANT_WRITE;
}

goto retry_read;
}
else if (ret < 0) {
Expand All @@ -382,6 +405,10 @@ int flb_tls_net_read(struct flb_tls_session *session, void *buf, size_t len)
return -1;
}

if (event_driven && io_tls_event_switch(session, MK_EVENT_READ) == -1) {
return -1;
}

return ret;
}

Expand Down
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