Improve the decoding of the third argument of the socket() call.

Decoding of the third argument depends on the first one. For doing this,
add a corresponding function to libsysdecode.

Thanks to jhb@ for suggesting this.

lib/libsysdecode/Makefile

@@ -22,6 +22,7 @@ MAN=	sysdecode.3 \
 	sysdecode_quotactl_cmd.3 \
 	sysdecode_sigcode.3 \
 	sysdecode_sockopt_name.3 \
+	sysdecode_socket_protocol.3 \
 	sysdecode_syscallnames.3 \
 	sysdecode_utrace.3
 MLINKS= sysdecode_abi_to_freebsd_errno.3 sysdecode_freebsd_to_abi_errno.3

lib/libsysdecode/flags.c

@@ -729,6 +729,19 @@ sysdecode_socketdomain(int domain)
 	return (lookup_value(sockdomain, domain));
 }
 
+const char *
+sysdecode_socket_protocol(int domain, int protocol)
+{
+
+	switch (domain) {
+	case PF_INET:
+	case PF_INET6:
+		return (lookup_value(sockipproto, protocol));
+	default:
+		return (NULL);
+	}
+}
+
 const char *
 sysdecode_sockaddr_family(int sa_family)
 {

lib/libsysdecode/sysdecode.h

@@ -99,6 +99,7 @@ const char *sysdecode_sigsegv_code(int _si_code);
 const char *sysdecode_sigtrap_code(int _si_code);
 const char *sysdecode_sockaddr_family(int _sa_family);
 const char *sysdecode_socketdomain(int _domain);
+const char *sysdecode_socket_protocol(int _domain, int _protocol);
 bool	sysdecode_socket_type(FILE *_fp, int _type, int *_rem);
 const char *sysdecode_sockopt_level(int _level);
 const char *sysdecode_sockopt_name(int _level, int _optname);

lib/libsysdecode/sysdecode_socket_protocol.3

@@ -0,0 +1,54 @@
+.\"
+.\" Copyright (c) 2016 John Baldwin <jhb@FreeBSD.org>
+.\" 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.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd May 25, 2017
+.Dt sysdecode_socket_protocol 3
+.Os
+.Sh NAME
+.Nm sysdecode_socket_protocol
+.Nd lookup name of socket protocol
+.Sh LIBRARY
+.Lb libsysdecode
+.Sh SYNOPSIS
+.In sys/types.h
+.In stdbool.h
+.In sysdecode.h
+.Ft const char *
+.Fn sysdecode_socket_protocol "int domain" "int protocol"
+.Sh DESCRIPTION
+The
+.Fn sysdecode_socket_protocol
+function returns a text description of the protocol passed in the
+.Fa protocol
+argument to
+.Xr socket 2 .
+.Fn sysdecode_socket_protocol
+takes the
+.Fa protocol
+as well as the
+.Fa domain
+to uniquely identify the protocol.

usr.bin/truss/syscalls.c

@@ -1938,13 +1938,20 @@ print_arg(struct syscall_args *sc, unsigned long *args, long *retval,
 		fprintf(fp, "%u", (socklen_t)args[sc->offset]);
 		break;
 	case Sockprotocol: {
-		int protocol;
+		const char *temp;
+		int domain, protocol;
 
+		domain = args[sc->offset - 2];
 		protocol = args[sc->offset];
 		if (protocol == 0) {
 			fputs("0", fp);
 		} else {
-			print_integer_arg(sysdecode_ipproto, fp, protocol);
+			temp = sysdecode_socket_protocol(domain, protocol);
+			if (temp) {
+				fputs(temp, fp);
+			} else {
+				fprintf(fp, "%d", protocol);
+			}
 		}
 		break;
 	}