[PATCH v3 13/16] netlink: introduce nla_decoder_t to parse netlink attribute data

JingPiao Chen chenjingpiao at gmail.com
Mon Jun 19 01:15:37 UTC 2017


* nlattr.h (nla_decoder_t): New typedef.
(DECL_NLA): New macro.
(decode_nlattr): Add decoders, size and opaque_data argument.
* nlattr.c: (decode_nlattr_with_data): Likewise.
(decode_nla_*): New functions.
* netlink_sock_diag.c (decode_inet_diag_req_compat)
(decode_inet_diag_req_v2, decode_inet_diag_msg)
(decode_netlink_diag_msg, (decode_packet_diag_msg)
(decode_smc_diag_msg, decode_unix_diag_msg): Add decoders,
size and opaque_data arguments. All callers updated.

Co-authored-by: Fabien Siron <fabien.siron at epita.fr>
---
 netlink_sock_diag.c | 21 ++++++++++++------
 nlattr.c            | 63 +++++++++++++++++++++++++++++++++++++++++++++++++----
 nlattr.h            | 27 +++++++++++++++++++++--
 3 files changed, 98 insertions(+), 13 deletions(-)

diff --git a/netlink_sock_diag.c b/netlink_sock_diag.c
index f46c441..57c2439 100644
--- a/netlink_sock_diag.c
+++ b/netlink_sock_diag.c
@@ -149,7 +149,8 @@ decode_unix_diag_msg(struct tcb *const tcp,
 	if (decode_nla && len > offset) {
 		tprints(", ");
 		decode_nlattr(tcp, addr + offset, len - offset,
-			      unix_diag_attrs, "UNIX_DIAG_???");
+			      unix_diag_attrs, "UNIX_DIAG_???",
+			      NULL, 0, NULL);
 	}
 }
 
@@ -238,7 +239,8 @@ decode_netlink_diag_msg(struct tcb *const tcp,
 	if (decode_nla && len > offset) {
 		tprints(", ");
 		decode_nlattr(tcp, addr + offset, len - offset,
-			      netlink_diag_attrs, "NETLINK_DIAG_???");
+			      netlink_diag_attrs, "NETLINK_DIAG_???",
+			      NULL, 0, NULL);
 	}
 }
 
@@ -309,7 +311,8 @@ decode_packet_diag_msg(struct tcb *const tcp,
 	if (decode_nla && len > offset) {
 		tprints(", ");
 		decode_nlattr(tcp, addr + offset, len - offset,
-			      packet_diag_attrs, "PACKET_DIAG_???");
+			      packet_diag_attrs, "PACKET_DIAG_???",
+			      NULL, 0, NULL);
 	}
 }
 
@@ -373,7 +376,8 @@ decode_inet_diag_req_compat(struct tcb *const tcp,
 	if (decode_nla && len > offset) {
 		tprints(", ");
 		decode_nlattr(tcp, addr + offset, len - offset,
-			      inet_diag_req_attrs, "INET_DIAG_REQ_???");
+			      inet_diag_req_attrs, "INET_DIAG_REQ_???",
+			      NULL, 0, NULL);
 	}
 }
 
@@ -417,7 +421,8 @@ decode_inet_diag_req_v2(struct tcb *const tcp,
 	if (decode_nla && len > offset) {
 		tprints(", ");
 		decode_nlattr(tcp, addr + offset, len - offset,
-			      inet_diag_req_attrs, "INET_DIAG_REQ_???");
+			      inet_diag_req_attrs, "INET_DIAG_REQ_???",
+			      NULL, 0, NULL);
 	}
 }
 
@@ -483,7 +488,8 @@ decode_inet_diag_msg(struct tcb *const tcp,
 	if (decode_nla && len > offset) {
 		tprints(", ");
 		decode_nlattr(tcp, addr + offset, len - offset,
-			      inet_diag_attrs, "INET_DIAG_???");
+			      inet_diag_attrs, "INET_DIAG_???",
+			      NULL, 0, NULL);
 	}
 }
 
@@ -563,7 +569,8 @@ decode_smc_diag_msg(struct tcb *const tcp,
 	if (decode_nla && len > offset) {
 		tprints(", ");
 		decode_nlattr(tcp, addr + offset, len - offset,
-			      smc_diag_attrs, "SMC_DIAG_???");
+			      smc_diag_attrs, "SMC_DIAG_???",
+			      NULL, 0, NULL);
 	}
 }
 #endif
diff --git a/nlattr.c b/nlattr.c
index eaf7e39..daa8261 100644
--- a/nlattr.c
+++ b/nlattr.c
@@ -28,6 +28,7 @@
  */
 
 #include "defs.h"
+#include "nlattr.h"
 
 #include <linux/netlink.h>
 
@@ -66,7 +67,10 @@ decode_nlattr_with_data(struct tcb *tcp,
 			kernel_ulong_t addr,
 			kernel_ulong_t len,
 			const struct xlat *const table,
-			const char *const dflt)
+			const char *const dflt,
+			const nla_decoder_t *decoders,
+			unsigned int size,
+			void *const opaque_data)
 {
 	unsigned int nla_len = nla->nla_len > len ? len : nla->nla_len;
 
@@ -77,7 +81,13 @@ decode_nlattr_with_data(struct tcb *tcp,
 
 	if (nla_len > NLA_HDRLEN) {
 		tprints(", ");
-		printstrn(tcp, addr + NLA_HDRLEN, nla_len - NLA_HDRLEN);
+		if (!decoders
+		    || nla->nla_type >= size
+		    || !decoders[nla->nla_type]
+		    || !decoders[nla->nla_type](tcp, addr + NLA_HDRLEN,
+						nla_len - NLA_HDRLEN,
+						opaque_data))
+			printstrn(tcp, addr + NLA_HDRLEN, len - NLA_HDRLEN);
 		tprints("}");
 	}
 }
@@ -87,7 +97,10 @@ decode_nlattr(struct tcb *const tcp,
 	      kernel_ulong_t addr,
 	      kernel_ulong_t len,
 	      const struct xlat *const table,
-	      const char *const dflt)
+	      const char *const dflt,
+	      const nla_decoder_t *decoders,
+	      unsigned int size,
+	      void *const opaque_data)
 {
 	struct nlattr nla;
 	bool print_array = false;
@@ -115,7 +128,8 @@ decode_nlattr(struct tcb *const tcp,
 			print_array = true;
 		}
 
-		decode_nlattr_with_data(tcp, &nla, addr, len, table, dflt);
+		decode_nlattr_with_data(tcp, &nla, addr, len, table, dflt,
+					decoders, size, opaque_data);
 
 		if (!next_addr)
 			break;
@@ -129,3 +143,44 @@ decode_nlattr(struct tcb *const tcp,
 		tprints("]");
 	}
 }
+
+bool
+decode_nla_str(struct tcb *tcp, kernel_ulong_t addr,
+	       kernel_ulong_t len, void *const opaque_data)
+{
+	printstr(tcp, addr);
+
+	return true;
+}
+
+bool
+decode_nla_strn(struct tcb *tcp, kernel_ulong_t addr,
+		kernel_ulong_t len, void *const opaque_data)
+{
+	printstrn(tcp, addr, len);
+
+	return true;
+}
+
+#define DECODE_NLA_INTEGER(name, type, fmt)				\
+bool									\
+decode_nla_ ## name(struct tcb *tcp, kernel_ulong_t addr,		\
+		    kernel_ulong_t len, void *const opaque_data)	\
+{									\
+	type num;							\
+									\
+	if (len < sizeof(num))						\
+		return false;						\
+	else if (!umove_or_printaddr(tcp, addr, &num))			\
+		tprintf(fmt, num);					\
+	return true;							\
+}
+
+DECODE_NLA_INTEGER(u8, uint8_t, "%" PRIu8)
+DECODE_NLA_INTEGER(u16, uint16_t, "%" PRIu16)
+DECODE_NLA_INTEGER(u32, uint32_t, "%" PRIu32)
+DECODE_NLA_INTEGER(u64, uint64_t, "%" PRIu64)
+DECODE_NLA_INTEGER(s8, int8_t, "%" PRId8)
+DECODE_NLA_INTEGER(s16, int16_t, "%" PRId16)
+DECODE_NLA_INTEGER(s32, int32_t, "%" PRId32)
+DECODE_NLA_INTEGER(s64, int64_t, "%" PRId64)
diff --git a/nlattr.h b/nlattr.h
index 6b94fc1..8501c4d 100644
--- a/nlattr.h
+++ b/nlattr.h
@@ -27,6 +27,29 @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+typedef bool (*nla_decoder_t)(struct tcb *, kernel_ulong_t addr,
+			      kernel_ulong_t len, void *opaque_data);
 extern void
-decode_nlattr(struct tcb *, kernel_ulong_t addr, kernel_ulong_t len,
-	      const struct xlat *, const char *);
+decode_nlattr(struct tcb *,
+	      kernel_ulong_t addr,
+	      kernel_ulong_t len,
+	      const struct xlat *,
+	      const char *,
+	      const nla_decoder_t *,
+	      unsigned int size,
+	      void *);
+
+#define DECL_NLA(name)					\
+extern bool						\
+decode_nla_ ## name(struct tcb *, kernel_ulong_t addr,	\
+		    kernel_ulong_t len, void *)
+DECL_NLA(u8);
+DECL_NLA(u16);
+DECL_NLA(u32);
+DECL_NLA(u64);
+DECL_NLA(s8);
+DECL_NLA(s16);
+DECL_NLA(s32);
+DECL_NLA(s64);
+DECL_NLA(str);
+DECL_NLA(strn);
-- 
2.7.4





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