uevent: parse the kernel object uevent socket and print the messages

.gitignore

@@ -13,3 +13,5 @@ debian/debhelper-build-stamp
 debian/files
 debian/*.substvars
 debian/safeboot
+*.o
+a.out

src/Makefile

@@ -0,0 +1,14 @@
+CFLAGS=-O3 -W -Wall
+CC=gcc
+O=../bin
+
+all: $O/uevent
+
+$O:
+	mkdir -p $O
+
+$O/uevent: uevent.o | $O
+	$(CC) $(LDFLAGS) -o $@ $^
+
+
+

src/uevent.c

@@ -0,0 +1,79 @@
+/*
+ * Listen to the kobject uevent netlink socket and print
+ * the messages to stdout as they arrive.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <linux/netlink.h>
+
+void hexdump(
+	const void * buf,
+	size_t len
+)
+{
+	for(size_t i = 0 ; i < len ; i++)
+		printf("%02x", ((const uint8_t*) buf)[i]);
+	printf("\n");
+}
+
+int main(void)
+{
+	int one_line = 0;
+
+	int sock = socket(PF_NETLINK, SOCK_RAW, NETLINK_KOBJECT_UEVENT);
+	if (sock < 0)
+	{
+		perror("netlink");
+		return EXIT_FAILURE;
+	}
+
+	struct sockaddr_nl src_addr = {
+		.nl_family	= AF_NETLINK,
+		.nl_pid		= getpid(),
+		.nl_groups	= 1,
+	};
+
+	if (bind(sock, (struct sockaddr*) &src_addr, sizeof(src_addr)) < 0)
+	{
+		perror("bind");
+		return EXIT_FAILURE;
+	}
+
+	uint8_t data[4096];
+
+	while(1)
+	{
+		ssize_t rc = recv(sock, data, sizeof(data), 0);
+		if (rc < 0)
+		{
+			perror("recv");
+			return EXIT_FAILURE;
+		}
+
+		if (one_line)
+		{
+			for(ssize_t i = 0 ; i < rc-1 ; i++)
+				if (data[i] == 0)
+					data[i] = '|';
+			printf("%s\n", (const char*) data);
+			continue;
+		}
+
+		ssize_t offset = 0;
+		while(offset < rc)
+		{
+			const char * msg = (const char *) &data[offset];
+			printf("%s%s\n",
+				offset == 0 ? "" : "\t",
+				msg
+			);
+
+			offset += strlen(msg) + 1;
+		}
+	}
+}