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in_forward: fix connection release on pause memory corruption [backport to 4.1] #11179

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Merged
merged 1 commit into from
Nov 19, 2025
+66 −6
Merged

in_forward: fix connection release on pause memory corruption [backport to 4.1] #11179

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27 changes: 26 additions & 1 deletion plugins/in_forward/fw.c
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Original file line number Diff line number Diff line change
Expand Up @@ -124,28 +124,37 @@ static int fw_unix_create(struct flb_in_fw_config *ctx)
static int in_fw_collect(struct flb_input_instance *ins,
struct flb_config *config, void *in_context)
{
int state_backup;
struct flb_connection *connection;
struct fw_conn *conn;
struct flb_in_fw_config *ctx;

ctx = in_context;

state_backup = ctx->state;
ctx->state = FW_INSTANCE_STATE_ACCEPTING_CLIENT;

connection = flb_downstream_conn_get(ctx->downstream);

if (connection == NULL) {
flb_plg_error(ctx->ins, "could not accept new connection");
ctx->state = state_backup;

return -1;
}

if (!config->is_ingestion_active) {
flb_downstream_conn_release(connection);
ctx->state = state_backup;

return -1;
}

if(ctx->is_paused) {
flb_downstream_conn_release(connection);
flb_plg_trace(ins, "TCP connection will be closed FD=%i", connection->fd);
ctx->state = state_backup;

return -1;
}

Expand All @@ -154,9 +163,17 @@ static int in_fw_collect(struct flb_input_instance *ins,
conn = fw_conn_add(connection, ctx);
if (!conn) {
flb_downstream_conn_release(connection);
ctx->state = state_backup;

return -1;
}

ctx->state = state_backup;

if (ctx->state == FW_INSTANCE_STATE_PAUSED) {
fw_conn_del_all(ctx);
}
Comment on lines +171 to +175
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@chatgpt-codex-connector chatgpt-codex-connector bot Nov 18, 2025

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P1 Badge Preserve paused state when accepting connections

During connection accept, in_fw_collect unconditionally restores ctx->state to the prior value at exit and immediately checks that restored value to decide whether to purge connections. If in_fw_pause sets ctx->state to FW_INSTANCE_STATE_PAUSED while a client is being accepted, this restore overwrites the paused state with the old RUNNING value and the subsequent fw_conn_del_all guard never fires, so the paused transition is lost and the just-accepted connection keeps processing traffic even though ingestion was paused to relieve backpressure. The state reset here should only occur when the state was not changed externally.

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return 0;
}

Expand Down Expand Up @@ -263,6 +280,7 @@ static int in_fw_init(struct flb_input_instance *ins,
return -1;
}

ctx->state = FW_INSTANCE_STATE_RUNNING;
ctx->coll_fd = -1;
ctx->ins = ins;
mk_list_init(&ctx->connections);
Expand Down Expand Up @@ -386,7 +404,10 @@ static void in_fw_pause(void *data, struct flb_config *config)
return;
}

fw_conn_del_all(ctx);
if (ctx->state == FW_INSTANCE_STATE_RUNNING) {
fw_conn_del_all(ctx);
}

ctx->is_paused = FLB_TRUE;
ret = pthread_mutex_unlock(&ctx->conn_mutex);
if (ret != 0) {
Expand All @@ -406,6 +427,8 @@ static void in_fw_pause(void *data, struct flb_config *config)
if (config->is_ingestion_active == FLB_FALSE) {
fw_conn_del_all(ctx);
}

ctx->state = FW_INSTANCE_STATE_PAUSED;
}

static void in_fw_resume(void *data, struct flb_config *config) {
Expand All @@ -427,6 +450,8 @@ static void in_fw_resume(void *data, struct flb_config *config) {
flb_plg_error(ctx->ins, "cannot unlock collector mutex");
return;
}

ctx->state = FW_INSTANCE_STATE_RUNNING;
}
}

Expand Down
8 changes: 8 additions & 0 deletions plugins/in_forward/fw.h
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,12 @@
#include <fluent-bit/flb_log_event_decoder.h>
#include <fluent-bit/flb_log_event_encoder.h>

#define FW_INSTANCE_STATE_RUNNING 0
#define FW_INSTANCE_STATE_ACCEPTING_CLIENT 1
#define FW_INSTANCE_STATE_PROCESSING_PACKET 2
#define FW_INSTANCE_STATE_PAUSED 3


enum {
FW_HANDSHAKE_HELO = 1,
FW_HANDSHAKE_PINGPONG = 2,
Expand Down Expand Up @@ -76,6 +82,8 @@ struct flb_in_fw_config {

pthread_mutex_t conn_mutex;

int state;

/* Plugin is paused */
int is_paused;
};
Expand Down
37 changes: 32 additions & 5 deletions plugins/in_forward/fw_conn.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,8 +28,7 @@
#include "fw_prot.h"
#include "fw_conn.h"

/* Callback invoked every time an event is triggered for a connection */
int fw_conn_event(void *data)
static int fw_conn_event_internal(struct flb_connection *connection)
{
int ret;
int bytes;
Expand All @@ -39,9 +38,6 @@ int fw_conn_event(void *data)
struct fw_conn *conn;
struct mk_event *event;
struct flb_in_fw_config *ctx;
struct flb_connection *connection;

connection = (struct flb_connection *) data;

conn = connection->user_data;

Expand Down Expand Up @@ -127,6 +123,37 @@ int fw_conn_event(void *data)
return 0;
}

/* Callback invoked every time an event is triggered for a connection */
int fw_conn_event(void *data)
{
struct flb_in_fw_config *ctx;
struct fw_conn *conn;
int result;
struct flb_connection *connection;
int state_backup;

connection = (struct flb_connection *) data;

conn = connection->user_data;

ctx = conn->ctx;

state_backup = ctx->state;

ctx->state = FW_INSTANCE_STATE_PROCESSING_PACKET;

result = fw_conn_event_internal(connection);

if (ctx->state == FW_INSTANCE_STATE_PROCESSING_PACKET) {
ctx->state = state_backup;
}
else if (ctx->state == FW_INSTANCE_STATE_PAUSED) {
fw_conn_del_all(ctx);
}

return result;
}

/* Create a new Forward request instance */
struct fw_conn *fw_conn_add(struct flb_connection *connection, struct flb_in_fw_config *ctx)
{
Expand Down