pping: Refactor json code and format

Use a JSON-writer library from iproute instead of complicated printf
statement. Also output timestamp, rtt and min_rtt as integers in
nanoseconds, rather than floats in seconds.

Signed-off-by: Simon Sundberg <simon.sundberg@kau.se>

lib/util/json_writer.c

@@ -0,0 +1,392 @@
+/* SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) */
+
+/* Copied from iproute2/lib/json_writer.c */
+
+/*
+ * Simple streaming JSON writer
+ *
+ * This takes care of the annoying bits of JSON syntax like the commas
+ * after elements
+ *
+ * Authors:	Stephen Hemminger <stephen@networkplumber.org>
+ */
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <assert.h>
+#include <malloc.h>
+#include <inttypes.h>
+#include <stdint.h>
+
+#include "json_writer.h"
+
+struct json_writer {
+	FILE		*out;	/* output file */
+	unsigned	depth;  /* nesting */
+	bool		pretty; /* optional whitepace */
+	char		sep;	/* either nul or comma */
+};
+
+/* indentation for pretty print */
+static void jsonw_indent(json_writer_t *self)
+{
+	unsigned i;
+	for (i = 0; i < self->depth; ++i)
+		fputs("    ", self->out);
+}
+
+/* end current line and indent if pretty printing */
+static void jsonw_eol(json_writer_t *self)
+{
+	if (!self->pretty)
+		return;
+
+	putc('\n', self->out);
+	jsonw_indent(self);
+}
+
+/* If current object is not empty print a comma */
+static void jsonw_eor(json_writer_t *self)
+{
+	if (self->sep != '\0')
+		putc(self->sep, self->out);
+	self->sep = ',';
+}
+
+
+/* Output JSON encoded string */
+/* Handles C escapes, does not do Unicode */
+static void jsonw_puts(json_writer_t *self, const char *str)
+{
+	putc('"', self->out);
+	for (; *str; ++str)
+		switch (*str) {
+		case '\t':
+			fputs("\\t", self->out);
+			break;
+		case '\n':
+			fputs("\\n", self->out);
+			break;
+		case '\r':
+			fputs("\\r", self->out);
+			break;
+		case '\f':
+			fputs("\\f", self->out);
+			break;
+		case '\b':
+			fputs("\\b", self->out);
+			break;
+		case '\\':
+			fputs("\\\\", self->out);
+			break;
+		case '"':
+			fputs("\\\"", self->out);
+			break;
+		case '\'':
+			fputs("\\\'", self->out);
+			break;
+		default:
+			putc(*str, self->out);
+		}
+	putc('"', self->out);
+}
+
+/* Create a new JSON stream */
+json_writer_t *jsonw_new(FILE *f)
+{
+	json_writer_t *self = malloc(sizeof(*self));
+	if (self) {
+		self->out = f;
+		self->depth = 0;
+		self->pretty = false;
+		self->sep = '\0';
+	}
+	return self;
+}
+
+/* End output to JSON stream */
+void jsonw_destroy(json_writer_t **self_p)
+{
+	json_writer_t *self = *self_p;
+
+	assert(self->depth == 0);
+	fputs("\n", self->out);
+	fflush(self->out);
+	free(self);
+	*self_p = NULL;
+}
+
+void jsonw_pretty(json_writer_t *self, bool on)
+{
+	self->pretty = on;
+}
+
+/* Basic blocks */
+static void jsonw_begin(json_writer_t *self, int c)
+{
+	jsonw_eor(self);
+	putc(c, self->out);
+	++self->depth;
+	self->sep = '\0';
+}
+
+static void jsonw_end(json_writer_t *self, int c)
+{
+	assert(self->depth > 0);
+
+	--self->depth;
+	if (self->sep != '\0')
+		jsonw_eol(self);
+	putc(c, self->out);
+	self->sep = ',';
+}
+
+
+/* Add a JSON property name */
+void jsonw_name(json_writer_t *self, const char *name)
+{
+	jsonw_eor(self);
+	jsonw_eol(self);
+	self->sep = '\0';
+	jsonw_puts(self, name);
+	putc(':', self->out);
+	if (self->pretty)
+		putc(' ', self->out);
+}
+
+__attribute__((format(printf, 2, 3)))
+void jsonw_printf(json_writer_t *self, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	jsonw_eor(self);
+	vfprintf(self->out, fmt, ap);
+	va_end(ap);
+}
+
+/* Collections */
+void jsonw_start_object(json_writer_t *self)
+{
+	jsonw_begin(self, '{');
+}
+
+void jsonw_end_object(json_writer_t *self)
+{
+	jsonw_end(self, '}');
+}
+
+void jsonw_start_array(json_writer_t *self)
+{
+	jsonw_begin(self, '[');
+	if (self->pretty)
+		putc(' ', self->out);
+}
+
+void jsonw_end_array(json_writer_t *self)
+{
+	if (self->pretty && self->sep)
+		putc(' ', self->out);
+	self->sep = '\0';
+	jsonw_end(self, ']');
+}
+
+/* JSON value types */
+void jsonw_string(json_writer_t *self, const char *value)
+{
+	jsonw_eor(self);
+	jsonw_puts(self, value);
+}
+
+void jsonw_bool(json_writer_t *self, bool val)
+{
+	jsonw_printf(self, "%s", val ? "true" : "false");
+}
+
+void jsonw_null(json_writer_t *self)
+{
+	jsonw_printf(self, "null");
+}
+
+void jsonw_float(json_writer_t *self, double num)
+{
+	jsonw_printf(self, "%g", num);
+}
+
+void jsonw_hhu(json_writer_t *self, unsigned char num)
+{
+	jsonw_printf(self, "%hhu", num);
+}
+
+void jsonw_hu(json_writer_t *self, unsigned short num)
+{
+	jsonw_printf(self, "%hu", num);
+}
+
+void jsonw_uint(json_writer_t *self, unsigned int num)
+{
+	jsonw_printf(self, "%u", num);
+}
+
+void jsonw_u64(json_writer_t *self, uint64_t num)
+{
+	jsonw_printf(self, "%"PRIu64, num);
+}
+
+void jsonw_xint(json_writer_t *self, uint64_t num)
+{
+	jsonw_printf(self, "%"PRIx64, num);
+}
+
+void jsonw_luint(json_writer_t *self, unsigned long num)
+{
+	jsonw_printf(self, "%lu", num);
+}
+
+void jsonw_lluint(json_writer_t *self, unsigned long long num)
+{
+	jsonw_printf(self, "%llu", num);
+}
+
+void jsonw_int(json_writer_t *self, int num)
+{
+	jsonw_printf(self, "%d", num);
+}
+
+void jsonw_s64(json_writer_t *self, int64_t num)
+{
+	jsonw_printf(self, "%"PRId64, num);
+}
+
+/* Basic name/value objects */
+void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
+{
+	jsonw_name(self, prop);
+	jsonw_string(self, val);
+}
+
+void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
+{
+	jsonw_name(self, prop);
+	jsonw_bool(self, val);
+}
+
+void jsonw_float_field(json_writer_t *self, const char *prop, double val)
+{
+	jsonw_name(self, prop);
+	jsonw_float(self, val);
+}
+
+void jsonw_uint_field(json_writer_t *self, const char *prop, unsigned int num)
+{
+	jsonw_name(self, prop);
+	jsonw_uint(self, num);
+}
+
+void jsonw_u64_field(json_writer_t *self, const char *prop, uint64_t num)
+{
+	jsonw_name(self, prop);
+	jsonw_u64(self, num);
+}
+
+void jsonw_xint_field(json_writer_t *self, const char *prop, uint64_t num)
+{
+	jsonw_name(self, prop);
+	jsonw_xint(self, num);
+}
+
+void jsonw_hhu_field(json_writer_t *self, const char *prop, unsigned char num)
+{
+	jsonw_name(self, prop);
+	jsonw_hhu(self, num);
+}
+
+void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num)
+{
+	jsonw_name(self, prop);
+	jsonw_hu(self, num);
+}
+
+void jsonw_luint_field(json_writer_t *self,
+			const char *prop,
+			unsigned long num)
+{
+	jsonw_name(self, prop);
+	jsonw_luint(self, num);
+}
+
+void jsonw_lluint_field(json_writer_t *self,
+			const char *prop,
+			unsigned long long num)
+{
+	jsonw_name(self, prop);
+	jsonw_lluint(self, num);
+}
+
+void jsonw_int_field(json_writer_t *self, const char *prop, int num)
+{
+	jsonw_name(self, prop);
+	jsonw_int(self, num);
+}
+
+void jsonw_s64_field(json_writer_t *self, const char *prop, int64_t num)
+{
+	jsonw_name(self, prop);
+	jsonw_s64(self, num);
+}
+
+void jsonw_null_field(json_writer_t *self, const char *prop)
+{
+	jsonw_name(self, prop);
+	jsonw_null(self);
+}
+
+#ifdef TEST
+int main(int argc, char **argv)
+{
+	json_writer_t *wr = jsonw_new(stdout);
+
+	jsonw_start_object(wr);
+	jsonw_pretty(wr, true);
+	jsonw_name(wr, "Vyatta");
+	jsonw_start_object(wr);
+	jsonw_string_field(wr, "url", "http://vyatta.com");
+	jsonw_uint_field(wr, "downloads", 2000000ul);
+	jsonw_float_field(wr, "stock", 8.16);
+
+	jsonw_name(wr, "ARGV");
+	jsonw_start_array(wr);
+	while (--argc)
+		jsonw_string(wr, *++argv);
+	jsonw_end_array(wr);
+
+	jsonw_name(wr, "empty");
+	jsonw_start_array(wr);
+	jsonw_end_array(wr);
+
+	jsonw_name(wr, "NIL");
+	jsonw_start_object(wr);
+	jsonw_end_object(wr);
+
+	jsonw_null_field(wr, "my_null");
+
+	jsonw_name(wr, "special chars");
+	jsonw_start_array(wr);
+	jsonw_string_field(wr, "slash", "/");
+	jsonw_string_field(wr, "newline", "\n");
+	jsonw_string_field(wr, "tab", "\t");
+	jsonw_string_field(wr, "ff", "\f");
+	jsonw_string_field(wr, "quote", "\"");
+	jsonw_string_field(wr, "tick", "\'");
+	jsonw_string_field(wr, "backslash", "\\");
+	jsonw_end_array(wr);
+
+	jsonw_end_object(wr);
+
+	jsonw_end_object(wr);
+	jsonw_destroy(&wr);
+	return 0;
+}
+
+#endif

lib/util/json_writer.h

@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) */
+
+/* Copied from iproute2/include/json_writer.h */
+
+/*
+ * Simple streaming JSON writer
+ *
+ * This takes care of the annoying bits of JSON syntax like the commas
+ * after elements
+ *
+ * Authors:	Stephen Hemminger <stephen@networkplumber.org>
+ */
+
+#ifndef _JSON_WRITER_H_
+#define _JSON_WRITER_H_
+
+#include <stdbool.h>
+#include <stdint.h>
+
+/* Opaque class structure */
+typedef struct json_writer json_writer_t;
+
+/* Create a new JSON stream */
+json_writer_t *jsonw_new(FILE *f);
+/* End output to JSON stream */
+void jsonw_destroy(json_writer_t **self_p);
+
+/* Cause output to have pretty whitespace */
+void jsonw_pretty(json_writer_t *self, bool on);
+
+/* Add property name */
+void jsonw_name(json_writer_t *self, const char *name);
+
+/* Add value  */
+__attribute__((format(printf, 2, 3)))
+void jsonw_printf(json_writer_t *self, const char *fmt, ...);
+void jsonw_string(json_writer_t *self, const char *value);
+void jsonw_bool(json_writer_t *self, bool value);
+void jsonw_float(json_writer_t *self, double number);
+void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num);
+void jsonw_uint(json_writer_t *self, unsigned int number);
+void jsonw_u64(json_writer_t *self, uint64_t number);
+void jsonw_xint(json_writer_t *self, uint64_t number);
+void jsonw_hhu(json_writer_t *self, unsigned char num);
+void jsonw_hu(json_writer_t *self, unsigned short number);
+void jsonw_int(json_writer_t *self, int number);
+void jsonw_s64(json_writer_t *self, int64_t number);
+void jsonw_null(json_writer_t *self);
+void jsonw_luint(json_writer_t *self, unsigned long num);
+void jsonw_lluint(json_writer_t *self, unsigned long long num);
+
+/* Useful Combinations of name and value */
+void jsonw_string_field(json_writer_t *self, const char *prop, const char *val);
+void jsonw_bool_field(json_writer_t *self, const char *prop, bool value);
+void jsonw_float_field(json_writer_t *self, const char *prop, double num);
+void jsonw_uint_field(json_writer_t *self, const char *prop, unsigned int num);
+void jsonw_u64_field(json_writer_t *self, const char *prop, uint64_t num);
+void jsonw_xint_field(json_writer_t *self, const char *prop, uint64_t num);
+void jsonw_hhu_field(json_writer_t *self, const char *prop, unsigned char num);
+void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num);
+void jsonw_int_field(json_writer_t *self, const char *prop, int num);
+void jsonw_s64_field(json_writer_t *self, const char *prop, int64_t num);
+void jsonw_null_field(json_writer_t *self, const char *prop);
+void jsonw_luint_field(json_writer_t *self, const char *prop,
+			unsigned long num);
+void jsonw_lluint_field(json_writer_t *self, const char *prop,
+			unsigned long long num);
+
+/* Collections */
+void jsonw_start_object(json_writer_t *self);
+void jsonw_end_object(json_writer_t *self);
+
+void jsonw_start_array(json_writer_t *self);
+void jsonw_end_array(json_writer_t *self);
+
+/* Override default exception handling */
+typedef void (jsonw_err_handler_fn)(const char *);
+
+#endif /* _JSON_WRITER_H_ */

lib/util/util.mk

@@ -1,2 +1,2 @@
 # list of objects in this directory
-UTIL_OBJS :=
+UTIL_OBJS := json_writer.o

pping/Makefile

@@ -3,7 +3,7 @@
 USER_TARGETS   := pping
 BPF_TARGETS    := pping_kern
 
-LDFLAGS    += -pthread
+LDLIBS     += -pthread
 EXTRA_DEPS += pping.h
 
 LIB_DIR = ../lib

pping/pping.c

@@ -23,6 +23,7 @@ static const char *__doc__ =
 #include <time.h>
 #include <pthread.h>
 
+#include "json_writer.h"
 #include "pping.h" //common structs for user-space and BPF parts
 
 #define NS_PER_SECOND 1000000000UL
@@ -83,7 +84,7 @@ struct pping_config {
 };
 
 static volatile int keep_running = 1;
-static bool json_started = false;
+static json_writer_t *json_ctx = NULL;
 
 static const struct option long_options[] = {
 	{ "help",             no_argument,       NULL, 'h' },
@@ -565,32 +566,25 @@ static void print_rtt_event_json(void *ctx, int cpu, void *data,
 	format_ip_address(saddr, sizeof(saddr), e->flow.ipv, &e->flow.saddr.ip);
 	format_ip_address(daddr, sizeof(daddr), e->flow.ipv, &e->flow.daddr.ip);
 
-	if (json_started) {
+	if (!json_ctx) {
-		printf(",");
+		json_ctx = jsonw_new(stdout);
-	} else {
+		jsonw_start_array(json_ctx);
-		printf("[");
-		json_started = true;
 	}
 
-	printf("\n{\"timestamp\":%llu.%09llu, \"rtt\":%llu.%09llu, "
+	jsonw_start_object(json_ctx);
-	       "\"min_rtt\":%llu.%09llu, \"src_ip\":\"%s\", \"src_port\":%d, "
+	jsonw_u64_field(json_ctx, "timestamp", time);
-	       "\"dest_ip\":\"%s\", \"dest_port\":%d, \"protocol\":\"%s\", "
+	jsonw_u64_field(json_ctx, "rtt", e->rtt);
-	       "\"sent_pkts\":%llu, \"sent_bytes\":%llu, \"rec_pkts\":%llu, "
+	jsonw_u64_field(json_ctx, "min_rtt", e->min_rtt);
-	       "\"rec_bytes\":%llu }",
+	jsonw_string_field(json_ctx, "src_ip", saddr);
-	       time / NS_PER_SECOND, time % NS_PER_SECOND,
+	jsonw_hu_field(json_ctx, "src_port", ntohs(e->flow.saddr.port));
-	       e->rtt / NS_PER_SECOND, e->rtt % NS_PER_SECOND,
+	jsonw_string_field(json_ctx, "dest_ip", daddr);
-	       e->min_rtt / NS_PER_SECOND, e->min_rtt % NS_PER_SECOND, saddr,
+	jsonw_hu_field(json_ctx, "dest_port", ntohs(e->flow.daddr.port));
-	       ntohs(e->flow.saddr.port), daddr, ntohs(e->flow.daddr.port),
+	jsonw_string_field(json_ctx, "protocol", proto_to_str(e->flow.proto));
-	       proto_to_str(e->flow.proto), e->sent_pkts, e->sent_bytes,
+	jsonw_u64_field(json_ctx, "sent_packets", e->sent_pkts);
-	       e->rec_pkts, e->rec_bytes);
+	jsonw_u64_field(json_ctx, "sent_bytes", e->sent_bytes);
-}
+	jsonw_u64_field(json_ctx, "rec_packets", e->rec_pkts);
-
+	jsonw_u64_field(json_ctx, "rec_bytes", e->rec_bytes);
-static void end_json_output(void)
+	jsonw_end_object(json_ctx);
-{
-	if (json_started)
-		printf("\n]\n");
-	else
-		printf("[]\n");
 }
 
 static void handle_missed_rtt_event(void *ctx, int cpu, __u64 lost_cnt)
@@ -797,9 +791,6 @@ int main(int argc, char *argv[])
 cleanup:
 	perf_buffer__free(pb);
 
-	if (config.json_format)
-		end_json_output();
-
 	if (xdp_attached) {
 		err = xdp_detach(config.ifindex, config.xdp_flags);
 		if (err)
@@ -825,5 +816,10 @@ cleanup:
 				config.pin_dir, strerror(-err));
 	}
 
+	if (config.json_format && json_ctx) {
+		jsonw_end_array(json_ctx);
+		jsonw_destroy(&json_ctx);
+	}
+
 	return err != 0;
 }