[PATCH v2] netlink: decode libudev netlink header

[Harsha Sharma]

* netlink.c: decode family NETLINK_KOBJECT_UEVENT
* netlink_kobject_uevent.h: New struct (udev_monitor_netlink_header)
* netlink_kobject_uevent.c: New file
* Makefile.am (strace_SOURCES): Add it
* defs.h: Add decode_netlink_kobject_uevent func

Changes in v2:
* New file netlink_kobject_uevent.c
* change location of netlink_kobject_uevent.h
* add comments in netlink_kobject_uevent.h
* add new files in Makefile.am
* add func decode_netlink_kobject_uevent in defs.h
* Use macros from print_fields.h instead of tprintf
* minor changes in decode_netlink_kobject_uevent (including name)

Signed-off-by: Harsha Sharma <harshasharmaiitr at gmail.com>
---
 Makefile.am              |  2 ++
 defs.h                   |  3 +++
 netlink.c                |  2 +-
 netlink_kobject_uevent.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++
 netlink_kobject_uevent.h | 29 ++++++++++++++++++++++++
 5 files changed, 93 insertions(+), 1 deletion(-)
 create mode 100644 netlink_kobject_uevent.c
 create mode 100644 netlink_kobject_uevent.h

diff --git a/Makefile.am b/Makefile.am
index 34da3372..9dace776 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -194,6 +194,8 @@ strace_SOURCES =	\
 	netlink.c       \
 	netlink.h	\
 	netlink_crypto.c \
+	netlink_kobject_uevent.c \
+	netlink_kobject_uevent.h \
 	netlink_sock_diag.h \
 	netlink_inet_diag.c \
 	netlink_netlink_diag.c \
diff --git a/defs.h b/defs.h
index bd4267b3..98d04dd5 100644
--- a/defs.h
+++ b/defs.h
@@ -687,6 +687,9 @@ DECL_NETLINK(route);
 DECL_NETLINK(selinux);
 DECL_NETLINK(sock_diag);
 
+extern void
+decode_netlink_kobject_uevent(struct tcb *, kernel_ulong_t addr,
+			      kernel_ulong_t len, const void *);
 extern int tv_nz(const struct timeval *);
 extern int tv_cmp(const struct timeval *, const struct timeval *);
 extern double tv_float(const struct timeval *);
diff --git a/netlink.c b/netlink.c
index 6b9a1f5c..e62e37d9 100644
--- a/netlink.c
+++ b/netlink.c
@@ -628,7 +628,7 @@ decode_netlink(struct tcb *const tcp,
 	const int family = get_fd_nl_family(tcp, fd);
 
 	if (family == NETLINK_KOBJECT_UEVENT) {
-		printstrn(tcp, addr, len);
+		decode_netlink_kobject_uevent(tcp, addr, len, NULL);
 		return;
 	}
 
diff --git a/netlink_kobject_uevent.c b/netlink_kobject_uevent.c
new file mode 100644
index 00000000..5b0e018d
--- /dev/null
+++ b/netlink_kobject_uevent.c
@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2018 Harsha Sharma <harshasharmaiittr at gmail.com>
+ * Copyright (c) 2017 The strace developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "defs.h"
+#include "netlink.h"
+#include "print_fields.h"
+#include "netlink_kobject_uevent.h"
+
+
+void
+decode_netlink_kobject_uevent(struct tcb *tcp, kernel_ulong_t addr,
+			      kernel_ulong_t len,
+			      const void *const opaque_data)
+{
+	struct udev_monitor_netlink_header uh;
+	const char *prefix = "libudev";
+
+	if (!umove_or_printaddr(tcp, addr, &uh) &&
+	    strcmp(uh.prefix, prefix) == 0) {
+		PRINT_FIELD_CSTRING("{", uh, prefix);
+		PRINT_FIELD_U(", ", uh, magic);
+		PRINT_FIELD_U(", ", uh, header_size);
+		PRINT_FIELD_U(", ", uh, properties_off);
+		PRINT_FIELD_U(", ", uh, properties_len);
+		PRINT_FIELD_U(", ", uh, filter_subsystem_hash);
+		PRINT_FIELD_U(", ", uh, filter_devtype_hash);
+		PRINT_FIELD_U(", ", uh, filter_tag_bloom_hi);
+		PRINT_FIELD_U(", ", uh, filter_tag_bloom_lo);
+		tprints("}");
+	} else {
+		printstrn(tcp, addr, len);
+	}
+}
diff --git a/netlink_kobject_uevent.h b/netlink_kobject_uevent.h
new file mode 100644
index 00000000..8b7c5970
--- /dev/null
+++ b/netlink_kobject_uevent.h
@@ -0,0 +1,29 @@
+#ifndef STRACE_NETLINK_KOBJECT_UEVENT_H
+#define STRACE_NETLINK_KOBJECT_UEVENT_H
+
+struct udev_monitor_netlink_header {
+	/* "libudev" prefix to distinguish libudev and kernel messages */
+	char prefix[8];
+	/*
+	 * magic to protect against daemon <-> library message format mismatch
+	 * used in the kernel from socket filter rules;
+	 * needs to be stored in network order
+	 */
+	unsigned int magic;
+	/* total length of header structure known to the sender */
+	unsigned int header_size;
+	/* properties string buffer */
+	unsigned int properties_off;
+	unsigned int properties_len;
+	/*
+	 * hashes of primary device properties strings,
+	 * to let libudev subscribers use in-kernel socket filters;
+	 * values need to be stored in network order
+	 */
+	unsigned int filter_subsystem_hash;
+	unsigned int filter_devtype_hash;
+	unsigned int filter_tag_bloom_hi;
+	unsigned int filter_tag_bloom_lo;
+};
+
+#endif /* !STRACE_NETLINK_KOBJECT_UEVENT_H */
-- 
2.11.0