Add and document ether_ntoa_r() and ether_aton_r() functions, which accept

passed storage buffers rather than using static storage.  Reimplement
ether_ntoa() and ether_aton() in terms of these functions.  These variants
are thread-safe.

2 files changed, 85 insertions, 37 deletions

diff --git a/lib/libc/net/ether_addr.c b/lib/libc/net/ether_addr.c
index c81e98a..d769f27 100644
--- a/lib/libc/net/ether_addr.c
+++ b/lib/libc/net/ether_addr.c
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 1995 Bill Paul <wpaul@ctr.columbia.edu>.
+ * Copyright (c) 2007 Robert N. M. Watson
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -67,53 +68,67 @@ __FBSDID("$FreeBSD$");
 int
 ether_line(const char *l, struct ether_addr *e, char *hostname)
 {
-        int i, o[6];
+	int i, o[6];
 
-        i = sscanf(l, "%x:%x:%x:%x:%x:%x %s", &o[0], &o[1], &o[2], &o[3],
+	i = sscanf(l, "%x:%x:%x:%x:%x:%x %s", &o[0], &o[1], &o[2], &o[3],
 	    &o[4], &o[5], hostname);
 	if (i != 7)
-                return (i);
-        for (i=0; i<6; i++)
-                e->octet[i] = o[i];
-        return (0);
+		return (i);
+	for (i=0; i<6; i++)
+		e->octet[i] = o[i];
+	return (0);
 }
 
 /*
  * Convert an ASCII representation of an ethernet address to binary form.
  */
 struct ether_addr *
-ether_aton(const char *a)
+ether_aton_r(const char *a, struct ether_addr *e)
 {
-        int i;
-	static struct ether_addr o;
+	int i;
 	unsigned int o0, o1, o2, o3, o4, o5;
 
-        i = sscanf(a, "%x:%x:%x:%x:%x:%x", &o0, &o1, &o2, &o3, &o4, &o5);
-        if (i != 6)
-                return (NULL);
-        o.octet[0]=o0;
-	o.octet[1]=o1;
-	o.octet[2]=o2;
-	o.octet[3]=o3;
-	o.octet[4]=o4;
-	o.octet[5]=o5;
-        return ((struct ether_addr *)&o);
+	i = sscanf(a, "%x:%x:%x:%x:%x:%x", &o0, &o1, &o2, &o3, &o4, &o5);
+	if (i != 6)
+		return (NULL);
+	e->octet[0]=o0;
+	e->octet[1]=o1;
+	e->octet[2]=o2;
+	e->octet[3]=o3;
+	e->octet[4]=o4;
+	e->octet[5]=o5;
+	return (e);
+}
+
+struct ether_addr *
+ether_aton(const char *a)
+{
+	static struct ether_addr e;
+
+	return (ether_aton_r(a, &e));
 }
 
 /*
  * Convert a binary representation of an ethernet address to an ASCII string.
  */
 char *
+ether_ntoa_r(const struct ether_addr *n, char *a)
+{
+	int i;
+
+	i = sprintf(a, "%02x:%02x:%02x:%02x:%02x:%02x", n->octet[0],
+	    n->octet[1], n->octet[2], n->octet[3], n->octet[4], n->octet[5]);
+	if (i < 17)
+		return (NULL);
+	return (a);
+}
+
+char *
 ether_ntoa(const struct ether_addr *n)
 {
-        int i;
 	static char a[18];
 
-        i = sprintf(a, "%02x:%02x:%02x:%02x:%02x:%02x", n->octet[0],
-	    n->octet[1], n->octet[2], n->octet[3], n->octet[4], n->octet[5]);
-        if (i < 17)
-                return (NULL);
-        return ((char *)&a);
+	return (ether_ntoa_r(n, a));
 }
 
 /*
diff --git a/lib/libc/net/ethers.3 b/lib/libc/net/ethers.3
index a132447..54d2149 100644
--- a/lib/libc/net/ethers.3
+++ b/lib/libc/net/ethers.3
@@ -1,5 +1,6 @@
-.\" Copyright (c) 1995
-.\"	Bill Paul <wpaul@ctr.columbia.edu>.  All rights reserved.
+.\" Copyright (c) 1995 Bill Paul <wpaul@ctr.columbia.edu>.
+.\" Copyright (c) 2007 Robert N. M. Watson
+.\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
@@ -30,14 +31,16 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 12, 1995
+.Dd May 13, 2007
 .Dt ETHERS 3
 .Os
 .Sh NAME
 .Nm ethers ,
 .Nm ether_line ,
 .Nm ether_aton ,
+.Nm ether_aton_r ,
 .Nm ether_ntoa ,
+.Nm ether_ntoa_r ,
 .Nm ether_ntohost ,
 .Nm ether_hostton
 .Nd Ethernet address conversion and lookup routines
@@ -51,8 +54,12 @@
 .Fn ether_line "const char *l" "struct ether_addr *e" "char *hostname"
 .Ft struct ether_addr *
 .Fn ether_aton "const char *a"
+.Ft struct ether_addr *
+.Fn ether_aton_r "const char *a" "struct ether_addr *e"
 .Ft char *
 .Fn ether_ntoa "const struct ether_addr *n"
+.Ft char *
+.Fn ether_ntoa_r "const struct ether_addr *n" "char *buf"
 .Ft int
 .Fn ether_ntohost "char *hostname" "const struct ether_addr *e"
 .Ft int
@@ -95,18 +102,23 @@ into their component parts.
 .Pp
 The
 .Fn ether_aton
-function converts an
+and
+.Fn ether_aton_r
+functions convert
 .Tn ASCII
-representation of an ethernet address into an
+representation of ethernet addresses into
 .Vt ether_addr
-structure.
-Likewise,
+structures.
+Likewise, the
 .Fn ether_ntoa
-converts an ethernet address specified as an
+and
+.Fn ether_ntoa_r
+functions
+convert ethernet addresses specified as
 .Vt ether_addr
-structure into an
+structures into
 .Tn ASCII
-string.
+strings.
 .Pp
 The
 .Fn ether_ntohost
@@ -138,7 +150,9 @@ and the hostname in the supplied string
 .Pp
 On success,
 .Fn ether_ntoa
-returns a pointer to a string containing an
+and
+.Fn ether_ntoa_r
+functions return a pointer to a string containing an
 .Tn ASCII
 representation of an ethernet address.
 If it is unable to convert
@@ -147,13 +161,25 @@ the supplied
 structure, it returns a
 .Dv NULL
 pointer.
+.Fn ether_ntoa
+stores the result in a static buffer;
+.Fn ether_ntoa_r
+stores the result in a user-passed buffer.
+.Pp
+
 Likewise,
 .Fn ether_aton
-returns a pointer to an
+and
+.Fn ether_aton_r
+return a pointer to an
 .Vt ether_addr
 structure on success and a
 .Dv NULL
 pointer on failure.
+.Fn ether_aton
+stores the result in a static buffer;
+.Fn ether_aton_r
+stores the result in a user-passed buffer.
 .Pp
 The
 .Fn ether_ntohost
@@ -192,6 +218,8 @@ This particular implementation of the
 .Nm
 library functions were written for and first appeared in
 .Fx 2.1 .
+Thread-safe function variants first appeared in
+.Fx 7.0 .
 .Sh BUGS
 The
 .Fn ether_aton
@@ -199,3 +227,8 @@ and
 .Fn ether_ntoa
 functions returns values that are stored in static memory areas
 which may be overwritten the next time they are called.
+.Pp
+.Fn ether_ntoa_r
+accepts a character buffer pointer, but not a buffer length.
+The caller must ensure adequate space is available in the buffer in order to
+avoid a buffer overflow.