Make the checks and adjustment of the snapshot length module-dependent.

Also, initialize the snapshot length to 0, meaning "not specified", so
that the default snapshot length, if not specified, is also
module-dependent.

That way, D-Bus has a maximum and default of 128MB, as that's the
maximum message size, but other capture devices have the current
MAXIMUM_SNAPLEN, so we can handle full-size D-Bus messages without
advertising an overly-large snapshot length for other devices,
potentially causing libpcap and programs using it or reading libpcap
files to allocate overly-large buffers for other capture devices.

1 files changed, 8 insertions, 0 deletions

diff --git a/pcap-dbus.c b/pcap-dbus.c
index ea3a390f..2fedaeff 100644
--- a/pcap-dbus.c
+++ b/pcap-dbus.c
@@ -223,6 +223,14 @@ dbus_activate(pcap_t *handle)
 		return PCAP_ERROR_RFMON_NOTSUP;
 	}
 
+	/*
+	 * Turn a negative snapshot value (invalid), a snapshot value of
+	 * 0 (unspecified), or a value bigger than the normal maximum
+	 * value, into the maximum message length for D-Bus (128MB).
+	 */
+	if (handle->snapshot <= 0 || handle->snapshot > 134217728)
+		handle->snapshot = 134217728;
+
 	/* dbus_connection_set_max_message_size(handlep->conn, handle->snapshot); */
 	if (handle->opt.buffer_size != 0)
 		dbus_connection_set_max_received_size(handlep->conn, handle->opt.buffer_size);