Changeset 509ee47 for lib/format_ndag.c

Timestamp:

12/10/18 14:52:43 (2 years ago)

Author:

Shane Alcock <salcock@…>

Branches:

develop

Children:

418c78d

Parents:

54ef438

Message:

Add option to allow users to specify a constant ERF framing length.

This can be useful for situations where

a) the input uses ERF (or some derivative thereof)
b) the link type and ERF record type are constant for the

duration of the capture

c) performance is critical

This option allows users to simply tell libtrace what the ERF
framing length on every packet is going to be, so libtrace
doesn't have to repeatedly derive the framing length for each
packet it processes. At high packet rates, the time taken to
do this calculation can really add up and it makes no sense
to risk dropping packets because you're busy calculating a value
that is always a single constant value.

File:

• lib/format_ndag.c (modified) (9 diffs)

lib/format_ndag.c

@@ -125 +125 @@
         pthread_t controlthread;
         libtrace_message_queue_t controlqueue;
+        int consterfframing;
 } ndag_format_data_t;
 
@@ -296 +297 @@
         FORMAT_DATA->nextthreadid = 0;
         FORMAT_DATA->receivers = NULL;
+        FORMAT_DATA->consterfframing = -1;
 
         scan = strchr(libtrace->uridata, ',');
@@ -316 +318 @@
                 FORMAT_DATA->portstr = strdup(scan + 1);
         }
+        return 0;
+}
+
+static int ndag_config_input(libtrace_t *libtrace, trace_option_t option,
+                void *value) {
+
+        switch(option) {
+                case TRACE_OPTION_CONSTANT_ERF_FRAMING:
+                        FORMAT_DATA->consterfframing = *(int *)value;
+                        break;
+                case TRACE_OPTION_EVENT_REALTIME:
+                case TRACE_OPTION_SNAPLEN:
+                case TRACE_OPTION_PROMISC:
+                case TRACE_OPTION_FILTER:
+                case TRACE_OPTION_META_FREQ:
+                default:
+                        trace_set_err(libtrace, TRACE_ERR_OPTION_UNAVAIL,
+                                        "Unsupported option");
+                        return -1;
+        }
+
         return 0;
 }
@@ -597 +620 @@
 }
 
-static int ndag_prepare_packet_stream(libtrace_t *libtrace,
-                recvstream_t *rt,
-                streamsock_t *ssock, libtrace_packet_t *packet,
-                uint32_t flags) {
+static int ndag_get_framing_length(const libtrace_packet_t *packet) {
+
+        libtrace_t *libtrace = packet->trace;
+
+        if (FORMAT_DATA->consterfframing >= 0) {
+                return FORMAT_DATA->consterfframing;
+        }
+        return erf_get_framing_length(packet);
+}
+
+static int ndag_prepare_packet_stream(libtrace_t *restrict libtrace,
+                recvstream_t *restrict rt,
+                streamsock_t *restrict ssock,
+                libtrace_packet_t *restrict packet,
+                uint32_t flags UNUSED) {
+
+        /* XXX flags is constant, so we can tell the compiler to not
+         * bother copying over the parameter
+         */
 
         dag_record_t *erfptr;
@@ -608 +646 @@
         uint16_t rlen;
 
+        /*
         if ((flags & TRACE_PREP_OWN_BUFFER) == TRACE_PREP_OWN_BUFFER) {
                 packet->buf_control = TRACE_CTRL_PACKET;
@@ -613 +652 @@
                 packet->buf_control = TRACE_CTRL_EXTERNAL;
         }
+        */
+        packet->buf_control = TRACE_CTRL_EXTERNAL;
 
         packet->trace = libtrace;
@@ -623 +664 @@
         if (erfptr->flags.rxerror == 1) {
                 packet->payload = NULL;
-                erfptr->rlen = htons(erf_get_framing_length(packet));
+                if (FORMAT_DATA->consterfframing >= 0) {
+                        erfptr->rlen = htons(FORMAT_DATA->consterfframing & 0xffff);
+                } else {
+                        erfptr->rlen = htons(erf_get_framing_length(packet));
+                }
         } else {
-                packet->payload = (char *)packet->buffer +
+                if (FORMAT_DATA->consterfframing >= 0) {
+                        packet->payload = (char *)packet->buffer +
+                                FORMAT_DATA->consterfframing;
+                } else {
+                        packet->payload = (char *)packet->buffer +
                                 erf_get_framing_length(packet);
+                }
         }
 
@@ -1453 +1503 @@
         NULL,                   /* probe magic */
         ndag_init_input,        /* init_input */
-        NULL,                   /* config_input */
+        ndag_config_input,      /* config_input */
         ndag_start_input,       /* start_input */
         ndag_pause_input,       /* pause_input */
@@ -1478 +1528 @@
         erf_get_capture_length, /* get_capture_length */
         erf_get_wire_length,    /* get_wire_length */
-        erf_get_framing_length, /* get_framing_length */
+        ndag_get_framing_length, /* get_framing_length */
         erf_set_capture_length, /* set_capture_length */
         NULL,                   /* get_received_packets */