[PATCH v18 14/15] log: add support for systemd journal

[Stephen Hemminger <stephen@networkplumber.org>]

If DPDK application is being run as a systemd service, then
it can use the journal protocol which allows putting more information
in the log such as priority and other information.

The use of journal protocol is automatically detected and
handled.  Rather than having a dependency on libsystemd,
just use the protocol directly as defined in:
	https://systemd.io/JOURNAL_NATIVE_PROTOCOL/

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/log/log.c | 154 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 152 insertions(+), 2 deletions(-)

diff --git a/lib/log/log.c b/lib/log/log.c
index ec0d55273e..650d294120 100644
--- a/lib/log/log.c
+++ b/lib/log/log.c
@@ -17,6 +17,10 @@
 #include <rte_os_shim.h>
 #else
 #include <syslog.h>
+#include <sys/uio.h>
+#include <sys/stat.h>
+#include <sys/socket.h>
+#include <sys/un.h>
 #endif
 
 #include <rte_log.h>
@@ -56,6 +60,7 @@ static struct rte_logs {
 	FILE *file;     /**< Output file set by rte_openlog_stream, or NULL. */
 #ifndef RTE_EXEC_ENV_WINDOWS
 	enum eal_log_syslog syslog_opt;
+	int journal_fd;
 #endif
 	log_print_t print_func;
 
@@ -775,6 +780,138 @@ static cookie_io_functions_t syslog_log_func = {
 	.close = syslog_log_close,
 };
 
+/*
+ * send message using journal protocol to journald
+ */
+static int
+journal_send(uint32_t level, const char *buf, size_t len)
+{
+	struct iovec iov[3];
+	char msg[] = "MESSAGE=";
+	char prio[32];
+	int ret;
+
+	iov[0].iov_base = msg;
+	iov[0].iov_len = strlen(msg);
+
+	iov[1].iov_base = (char *)(uintptr_t)buf;
+	iov[1].iov_len = len;
+
+	/* priority value between 0 ("emerg") and 7 ("debug") */
+	iov[2].iov_base = prio;
+	iov[2].iov_len = snprintf(prio, sizeof(prio),
+				  "PRIORITY=%i\n", level - 1);
+
+	ret = writev(rte_logs.journal_fd, iov, 3);
+	return ret;
+}
+
+__rte_format_printf(3, 0)
+static int
+journal_print(FILE *f __rte_unused, uint32_t level, const char *format, va_list ap)
+{
+	char buf[BUFSIZ];
+	size_t len;
+
+	len = vsnprintf(buf, sizeof(buf), format, ap);
+	if (len == 0)
+		return 0;
+
+	/* check for truncation */
+	if (len >= sizeof(buf) - 1)
+		len = sizeof(buf) - 1;
+
+	/* check that message ends with newline, if not add one */
+	if (buf[len - 1] != '\n')
+		buf[len++] = '\n';
+
+	return journal_send(level, buf, len);
+}
+
+/* wrapper for log stream to put messages into journal */
+static ssize_t
+journal_log_write(__rte_unused void *c, const char *buf, size_t size)
+{
+	return journal_send(rte_log_cur_msg_loglevel(), buf, size);
+}
+
+static cookie_io_functions_t journal_log_func = {
+	.write = journal_log_write,
+};
+
+/*
+ * Check if stderr is going to system journal.
+ * This is the documented way to handle systemd journal
+ *
+ * See: https://systemd.io/JOURNAL_NATIVE_PROTOCOL/
+ *
+ */
+static bool
+is_journal(int fd)
+{
+	char *jenv, *endp = NULL;
+	struct stat st;
+	unsigned long dev, ino;
+
+	jenv = getenv("JOURNAL_STREAM");
+	if (jenv == NULL)
+		return false;
+
+	if (fstat(fd, &st) < 0)
+		return false;
+
+	/* systemd sets colon-separated list of device and inode number */
+	dev = strtoul(jenv, &endp, 10);
+	if (endp == NULL || *endp != ':')
+		return false;	/* missing colon */
+
+	ino = strtoul(endp + 1, NULL, 10);
+
+	return dev == st.st_dev && ino == st.st_ino;
+}
+
+/* Connect to systemd's journal service */
+static int
+open_journal(const char *id)
+{
+	char *syslog_id = NULL;
+	struct sockaddr_un sun = {
+		.sun_family = AF_UNIX,
+		.sun_path = "/run/systemd/journal/socket",
+	};
+	ssize_t len;
+	int s;
+
+	s = socket(AF_UNIX, SOCK_DGRAM, 0);
+	if (s < 0)
+		return -1;
+
+	if (connect(s, (struct sockaddr *)&sun, sizeof(sun)) < 0)
+		goto error;
+
+	/* Send syslog identifier as first message */
+	len = asprintf(&syslog_id, "SYSLOG_IDENTIFIER=%s\n", id);
+	if (len == 0)
+		goto error;
+
+	if (write(s, syslog_id, len) != len)
+		goto error;
+
+	free(syslog_id);
+
+	/* redirect other log messages to journal */
+	FILE *log_stream = fopencookie(NULL, "w", journal_log_func);
+	if (log_stream != NULL)
+		default_log_stream = log_stream;
+
+	return s;
+
+error:
+	free(syslog_id);
+	close(s);
+	return -1;
+}
+
 static void
 log_open_syslog(const char *id, bool is_terminal)
 {
@@ -797,11 +934,24 @@ log_open_syslog(const char *id, bool is_terminal)
 static void
 log_output_selection(const char *id)
 {
+#ifdef RTE_EXEC_ENV_WINDOWS
 	RTE_SET_USED(id);
-
-#ifndef RTE_EXEC_ENV_WINDOWS
+#else
 	bool is_terminal = isatty(STDERR_FILENO);
 
+	/* If stderr is redirected to systemd journal then upgrade */
+	if (!is_terminal && is_journal(STDERR_FILENO)) {
+		int jfd = open_journal(id);
+
+		if (jfd < 0) {
+			RTE_LOG_LINE(NOTICE, EAL, "Cannot connect to journal: %s",
+				     strerror(errno));
+		} else {
+			rte_logs.print_func = journal_print;
+			return;
+		}
+	}
+
 	if (using_syslog(is_terminal)) {
 		log_open_syslog(id, is_terminal);
 		return;
-- 
2.43.0