log: syslog driver

Provide a log driver that broadcasts RFC 3164 messages to syslog servers.
rsyslog is one implementation of such a server.

The messages are sent to the local broadcast address 255.255.255.255 on
port 514.

The environment variable log_hostname can be used to provide the HOSTNAME
field for the messages. The optional TIMESTAMP field of RFC 3164 is not
provided.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

MAINTAINERS

@@ -654,7 +654,7 @@ LOGGING
 M:	Simon Glass <sjg@chromium.org>
 S:	Maintained
 T:	git https://gitlab.denx.de/u-boot/u-boot.git
-F:	common/log.c
+F:	common/log*
 F:	cmd/log.c
 F:	test/log/log_test.c
 F:	test/py/tests/test_log.py

common/Kconfig

@@ -775,6 +775,13 @@ config TPL_LOG_CONSOLE
 	  log message is shown - other details like level, category, file and
 	  line number are omitted.
 
+config LOG_SYSLOG
+	bool "Log output to syslog server"
+	depends on LOG && NET
+	help
+	  Enables a log driver which broadcasts log records via UDP port 514
+	  to syslog servers.
+
 config LOG_TEST
 	bool "Provide a test for logging"
 	depends on LOG && UNIT_TEST

common/Makefile

@@ -132,6 +132,7 @@ obj-$(CONFIG_DFU_OVER_USB) += dfu.o
 obj-y += command.o
 obj-$(CONFIG_$(SPL_TPL_)LOG) += log.o
 obj-$(CONFIG_$(SPL_TPL_)LOG_CONSOLE) += log_console.o
+obj-$(CONFIG_$(SPL_TPL_)LOG_SYSLOG) += log_syslog.o
 obj-y += s_record.o
 obj-$(CONFIG_CMD_LOADB) += xyzModem.o
 obj-$(CONFIG_$(SPL_TPL_)YMODEM_SUPPORT) += xyzModem.o

common/log_syslog.c

@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Log to syslog.
+ *
+ * Copyright (c) 2020, Heinrich Schuchardt <xypron.glpk@gmx.de>
+ */
+
+#include <common.h>
+#include <log.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+#define BUFFER_SIZE 480
+
+static void append(char **buf, char *buf_end, const char *fmt, ...)
+{
+	va_list args;
+	size_t size = buf_end - *buf;
+
+	va_start(args, fmt);
+	vsnprintf(*buf, size, fmt, args);
+	va_end(args);
+	*buf += strlen(*buf);
+}
+
+static int log_syslog_emit(struct log_device *ldev, struct log_rec *rec)
+{
+	int ret;
+	int fmt = gd->log_fmt;
+	char msg[BUFFER_SIZE];
+	char *msg_end = msg + BUFFER_SIZE;
+	char *ptr = msg;
+	char *iphdr;
+	char *log_msg;
+	int eth_hdr_size;
+	struct in_addr bcast_ip;
+	static int processing_msg;
+	unsigned int log_level;
+	char *log_hostname;
+
+	/* Fend off messages from the network stack while writing a message */
+	if (processing_msg)
+		return 0;
+
+	processing_msg = 1;
+
+	/* Setup packet buffers */
+	net_init();
+	/* Disable hardware and put it into the reset state */
+	eth_halt();
+	/* Set current device according to environment variables */
+	eth_set_current();
+	/* Get hardware ready for send and receive operations */
+	ret = eth_init();
+	if (ret < 0) {
+		eth_halt();
+		goto out;
+	}
+
+	memset(msg, 0, BUFFER_SIZE);
+
+	/* Set ethernet header */
+	eth_hdr_size = net_set_ether((uchar *)ptr, net_bcast_ethaddr, PROT_IP);
+	ptr += eth_hdr_size;
+	iphdr = ptr;
+	ptr += IP_UDP_HDR_SIZE;
+	log_msg = ptr;
+
+	/*
+	 * The syslog log levels defined in RFC 5424 match the U-Boot ones up to
+	 * level 7 (debug).
+	 */
+	log_level = rec->level;
+	if (log_level > 7)
+		log_level = 7;
+	/* Leave high bits as 0 to write a 'kernel message' */
+
+	/* Write log message to buffer */
+	append(&ptr, msg_end, "<%u>", log_level);
+	log_hostname = env_get("log_hostname");
+	if (log_hostname)
+		append(&ptr, msg_end, "%s ", log_hostname);
+	append(&ptr, msg_end, "uboot: ");
+	if (fmt & (1 << LOGF_LEVEL))
+		append(&ptr, msg_end, "%s.",
+		       log_get_level_name(rec->level));
+	if (fmt & (1 << LOGF_CAT))
+		append(&ptr, msg_end, "%s,",
+		       log_get_cat_name(rec->cat));
+	if (fmt & (1 << LOGF_FILE))
+		append(&ptr, msg_end, "%s:", rec->file);
+	if (fmt & (1 << LOGF_LINE))
+		append(&ptr, msg_end, "%d-", rec->line);
+	if (fmt & (1 << LOGF_FUNC))
+		append(&ptr, msg_end, "%s()", rec->func);
+	if (fmt & (1 << LOGF_MSG))
+		append(&ptr, msg_end, "%s%s",
+		       fmt != (1 << LOGF_MSG) ? " " : "", rec->msg);
+	/* Consider trailing 0x00 */
+	ptr++;
+
+	debug("log message: '%s'\n", log_msg);
+
+	/* Broadcast message */
+	bcast_ip.s_addr = 0xFFFFFFFFL;
+	net_set_udp_header((uchar *)iphdr, bcast_ip, 514, 514, ptr - log_msg);
+	net_send_packet((uchar *)msg, ptr - msg);
+
+out:
+	processing_msg = 0;
+	return ret;
+}
+
+LOG_DRIVER(syslog) = {
+	.name	= "syslog",
+	.emit	= log_syslog_emit,
+};

doc/README.log

@@ -147,7 +147,10 @@ several possible determinations for logging information, all of which can be
 enabled or disabled independently:
 
    console - goes to stdout
+   syslog - broadcast RFC 3164 messages to syslog servers on UDP port 514
 
+The syslog driver sends the value of environmental variable 'log_hostname' as
+HOSTNAME if available.
 
 Log format
 ----------