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Improve socket error detection in unicast transport read #1162

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f95698a
Improve socket error detection in unicast transport read
sashacmc Feb 19, 2026
b24c8a3
Fix TLS to be consistent with TCP changes
sashacmc Feb 20, 2026
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8 changes: 6 additions & 2 deletions src/link/unicast/tls.c
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Original file line number Diff line number Diff line change
Expand Up @@ -179,9 +179,13 @@ static size_t _z_f_link_read_exact_tls(const _z_link_t *self, uint8_t *ptr, size
rb = _z_read_tls(&self->_socket._tls, &ptr[n], len - n);
}

if (rb == SIZE_MAX) {
n = rb;
if (rb == 0) {
// Socket closed
n = 0;
break;
} else if (rb == SIZE_MAX) {
// WANT_READ or timeout - continue loop to retry
continue;
}
n += rb;
} while (n != len);
Expand Down
6 changes: 4 additions & 2 deletions src/system/unix/tls.c
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Original file line number Diff line number Diff line change
Expand Up @@ -662,11 +662,13 @@ size_t _z_read_tls(const _z_tls_socket_t *sock, uint8_t *ptr, size_t len) {
}

if (ret == MBEDTLS_ERR_SSL_WANT_READ || ret == MBEDTLS_ERR_SSL_WANT_WRITE) {
return 0;
// Like EAGAIN from recv() with SO_RCVTIMEO
return SIZE_MAX;
}

if (ret == 0 || ret == MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY || ret == MBEDTLS_ERR_SSL_CONN_EOF) {
return SIZE_MAX;
// Connection closed gracefully, like TCP recv() returning 0
return 0;
}

_Z_ERROR("TLS read error: %d", ret);
Expand Down
56 changes: 43 additions & 13 deletions src/transport/unicast/read.c
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Original file line number Diff line number Diff line change
Expand Up @@ -74,39 +74,54 @@ static z_result_t _z_unicast_process_messages(_z_transport_unicast_t *ztu, _z_tr
return _Z_RES_OK;
}

static bool _z_unicast_client_read(_z_transport_unicast_t *ztu, _z_transport_peer_unicast_t *peer, size_t *to_read) {
static int _z_unicast_client_read(_z_transport_unicast_t *ztu, _z_transport_peer_unicast_t *peer, size_t *to_read) {
switch (ztu->_common._link->_cap._flow) {
case Z_LINK_CAP_FLOW_STREAM:
if (_z_zbuf_len(&ztu->_common._zbuf) < _Z_MSG_LEN_ENC_SIZE) {
_z_link_socket_recv_zbuf(ztu->_common._link, &ztu->_common._zbuf, peer->_socket);
size_t rb = _z_link_socket_recv_zbuf(ztu->_common._link, &ztu->_common._zbuf, peer->_socket);
if (rb == SIZE_MAX) {
return _Z_UNICAST_PEER_READ_STATUS_PENDING_DATA;
}
if (rb == 0) {
return _Z_UNICAST_PEER_READ_STATUS_SOCKET_CLOSED;
}
if (_z_zbuf_len(&ztu->_common._zbuf) < _Z_MSG_LEN_ENC_SIZE) {
_z_zbuf_compact(&ztu->_common._zbuf);
return false;
return _Z_UNICAST_PEER_READ_STATUS_PENDING_DATA;
}
}
// Get stream size
*to_read = _z_read_stream_size(&ztu->_common._zbuf);
// Read data
if (_z_zbuf_len(&ztu->_common._zbuf) < *to_read) {
_z_link_socket_recv_zbuf(ztu->_common._link, &ztu->_common._zbuf, peer->_socket);
size_t rb = _z_link_socket_recv_zbuf(ztu->_common._link, &ztu->_common._zbuf, peer->_socket);
if (rb == SIZE_MAX) {
return _Z_UNICAST_PEER_READ_STATUS_PENDING_DATA;
}
if (rb == 0) {
return _Z_UNICAST_PEER_READ_STATUS_SOCKET_CLOSED;
}
if (_z_zbuf_len(&ztu->_common._zbuf) < *to_read) {
_z_zbuf_set_rpos(&ztu->_common._zbuf, _z_zbuf_get_rpos(&ztu->_common._zbuf) - _Z_MSG_LEN_ENC_SIZE);
_z_zbuf_compact(&ztu->_common._zbuf);
return false;
return _Z_UNICAST_PEER_READ_STATUS_PENDING_DATA;
}
}
break;
case Z_LINK_CAP_FLOW_DATAGRAM:
_z_zbuf_compact(&ztu->_common._zbuf);
*to_read = _z_link_socket_recv_zbuf(ztu->_common._link, &ztu->_common._zbuf, peer->_socket);
if (*to_read == SIZE_MAX) {
return false;
return _Z_UNICAST_PEER_READ_STATUS_PENDING_DATA;
}
if (*to_read == 0) {
return _Z_UNICAST_PEER_READ_STATUS_SOCKET_CLOSED;
}
break;
default:
break;
}
return true;
return _Z_UNICAST_PEER_READ_STATUS_OK;
}

z_result_t _zp_unicast_read(_z_transport_unicast_t *ztu, bool single_read) {
Expand All @@ -128,11 +143,15 @@ z_result_t _zp_unicast_read(_z_transport_unicast_t *ztu, bool single_read) {
_z_zbuf_reset(&ztu->_common._zbuf);
size_t to_read = 0;
// Retrieve data if any
if (_z_unicast_client_read(ztu, curr_peer, &to_read)) {
int read_status = _z_unicast_client_read(ztu, curr_peer, &to_read);
if (read_status == _Z_UNICAST_PEER_READ_STATUS_OK) {
// Process data
_Z_RETURN_IF_ERR(_z_unicast_process_messages(ztu, curr_peer, to_read))
} else {
} else if (read_status == _Z_UNICAST_PEER_READ_STATUS_PENDING_DATA) {
return _Z_NO_DATA_PROCESSED;
} else {
// Socket closed or critical error
_Z_ERROR_RETURN(_Z_ERR_TRANSPORT_RX_FAILED);
}
}
return _Z_RES_OK;
Expand Down Expand Up @@ -257,6 +276,9 @@ static int _z_unicast_peer_read(_z_transport_unicast_t *ztu, _z_transport_peer_u
if (*to_read == SIZE_MAX) {
return _Z_UNICAST_PEER_READ_STATUS_PENDING_DATA;
}
if (*to_read == 0) {
return _Z_UNICAST_PEER_READ_STATUS_SOCKET_CLOSED;
}
break;
default:
break;
Expand Down Expand Up @@ -360,11 +382,19 @@ void *_zp_unicast_read_task(void *ztu_arg) {
{
size_t to_read = 0;
// Retrieve data
if (!_z_unicast_client_read(ztu, curr_peer, &to_read)) {
int read_status = _z_unicast_client_read(ztu, curr_peer, &to_read);
if (read_status == _Z_UNICAST_PEER_READ_STATUS_OK) {
// Process data
if (_z_unicast_process_messages(ztu, curr_peer, to_read) != _Z_RES_OK) {
ztu->_common._read_task_running = false;
continue;
}
} else if (read_status == _Z_UNICAST_PEER_READ_STATUS_PENDING_DATA) {
// No data available yet, continue loop
continue;
}
// Process data
if (_z_unicast_process_messages(ztu, curr_peer, to_read) != _Z_RES_OK) {
} else {
// Socket closed or critical error - exit task to allow reconnection
_Z_ERROR("Connection closed or error detected, exiting read task");
ztu->_common._read_task_running = false;
continue;
}
Expand Down
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