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On 2010/01/26 08:40, John Baldwin wrote:
> I just have two suggestions/comments:
> @@ -295,6 +295,7 @@ struct      ifreq {
[...]
> I prefer to not have this all on one line, but to instead be:
[...]
> Even better would be to actually define a separate type earlier
> in the file I think:
[...]
> I think caddr_t is deprecated in favor of void * for new APIs at least.

I have split it into another type and used void *, also updated the
manual page.

> Second, it would be nice if SIOCGIFDESCR provided length feedback to userland
> similar to sysctl(3).  Maybe change the code to set ifr.ifr_buffer.length to
> the required length when returning ENAMETOOLONG.  Userland can then just skip
> to that length directly, or instead use an idiom similar to sysctl where it
> does the following:

Done in a slightly different way.  It seems to be slightly wasteful (not
a big deal, though) to ioctl every time to obtain the length, so I used
an arbitrary number (2^6) and make the program to adapt to larger number
if kernel gave feedback with ENAMETOOLONG, and the buffer/length would
be used the next call.

Cheers,
- -- 
Xin LI <delp...@delphij.net>    http://www.delphij.net/
FreeBSD - The Power to Serve!          Live free or die
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Index: contrib/libpcap/inet.c
===================================================================
--- contrib/libpcap/inet.c      (revision 203021)
+++ contrib/libpcap/inet.c      (working copy)
@@ -401,11 +401,16 @@ add_addr_to_iflist(pcap_if_t **alldevs, const char
        pcap_if_t *curdev;
        char *description = NULL;
        pcap_addr_t *curaddr, *prevaddr, *nextaddr;
+       int s;
 #ifdef SIOCGIFDESCR
        struct ifreq ifrdesc;
+#ifndef IFDESCRSIZE
+#define _IFDESCRSIZE 64
+       char ifdescr[_IFDESCRSIZE];
+#else
        char ifdescr[IFDESCRSIZE];
-       int s;
 #endif
+#endif
 
 #ifdef SIOCGIFDESCR
        /*
@@ -413,12 +418,17 @@ add_addr_to_iflist(pcap_if_t **alldevs, const char
         */
        memset(&ifrdesc, 0, sizeof ifrdesc);
        strlcpy(ifrdesc.ifr_name, name, sizeof ifrdesc.ifr_name);
+#ifdef __FreeBSD__
+       ifrdesc.ifr_buffer.buffer = ifdescr;
+       ifrdesc.ifr_buffer.length = sizeof(ifdescr);
+#else
        ifrdesc.ifr_data = (caddr_t)&ifdescr;
+#endif
        s = socket(AF_INET, SOCK_DGRAM, 0);
        if (s >= 0) {
                if (ioctl(s, SIOCGIFDESCR, &ifrdesc) == 0 &&
-                   strlen(ifrdesc.ifr_data) != 0)
-                       description = ifrdesc.ifr_data;
+                   strlen(ifdescr) != 0)
+                       description = ifdescr;
                close(s);
        }
 #endif
Index: sbin/ifconfig/ifconfig.8
===================================================================
--- sbin/ifconfig/ifconfig.8    (revision 203021)
+++ sbin/ifconfig/ifconfig.8    (working copy)
@@ -28,7 +28,7 @@
 .\"     From: @(#)ifconfig.8   8.3 (Berkeley) 1/5/94
 .\" $FreeBSD$
 .\"
-.Dd September 23, 2009
+.Dd January 26, 2010
 .Dt IFCONFIG 8
 .Os
 .Sh NAME
@@ -258,6 +258,12 @@ Disable permanently promiscuous mode.
 Another name for the
 .Fl alias
 parameter.
+.It Cm description Ar value , Cm descr Ar value
+Specify a description of the interface.
+This can be used to label interfaces in situations where they may
+otherwise be difficult to distinguish.
+.It Cm -description , Cm -descr
+Clear the interface description.
 .It Cm down
 Mark an interface
 .Dq down .
@@ -2512,6 +2518,10 @@ Configure the interface
 to use 100baseTX, full duplex Ethernet media options:
 .Dl # ifconfig xl0 media 100baseTX mediaopt full-duplex
 .Pp
+Label the em0 interface as an uplink:
+.Pp
+.Dl # ifconfig em0 description \&"Uplink to Gigabit Switch 2\&"
+.Pp
 Create the software network interface
 .Li gif1 :
 .Dl # ifconfig gif1 create
Index: sbin/ifconfig/ifconfig.c
===================================================================
--- sbin/ifconfig/ifconfig.c    (revision 203021)
+++ sbin/ifconfig/ifconfig.c    (working copy)
@@ -44,7 +44,6 @@ static const char rcsid[] =
 #include <sys/param.h>
 #include <sys/ioctl.h>
 #include <sys/socket.h>
-#include <sys/sysctl.h>
 #include <sys/time.h>
 #include <sys/module.h>
 #include <sys/linker.h>
@@ -83,6 +82,8 @@ static const char rcsid[] =
 struct ifreq ifr;
 
 char   name[IFNAMSIZ];
+char   *descr = NULL;
+size_t descrlen = 64;
 int    setaddr;
 int    setmask;
 int    doalias;
@@ -838,6 +839,40 @@ setifname(const char *val, int dummy __unused, int
        free(newname);
 }
 
+/* ARGSUSED */
+static void
+setifdescr(const char *val, int dummy __unused, int s, 
+    const struct afswtch *afp)
+{
+       char *newdescr;
+
+       ifr.ifr_buffer.length = strlen(val) + 1;
+       if (ifr.ifr_buffer.length == 1) {
+               ifr.ifr_buffer.buffer = newdescr = NULL;
+               ifr.ifr_buffer.length = 0;
+       } else {
+               newdescr = strdup(val);
+               ifr.ifr_buffer.buffer = newdescr;
+               if (newdescr == NULL) {
+                       warn("no memory to set ifdescr");
+                       return;
+               }
+       }
+
+       if (ioctl(s, SIOCSIFDESCR, (caddr_t)&ifr) < 0)
+               warn("ioctl (set descr)");
+
+       free(newdescr);
+}
+
+/* ARGSUSED */
+static void
+unsetifdescr(const char *val, int value, int s, const struct afswtch *afp)
+{
+
+       setifdescr("", 0, s, 0);
+}
+
 #define        IFFBITS \
 "\020\1UP\2BROADCAST\3DEBUG\4LOOPBACK\5POINTOPOINT\6SMART\7RUNNING" \
 "\10NOARP\11PROMISC\12ALLMULTI\13OACTIVE\14SIMPLEX\15LINK0\16LINK1\17LINK2" \
@@ -882,6 +917,25 @@ status(const struct afswtch *afp, const struct soc
                printf(" mtu %d", ifr.ifr_mtu);
        putchar('\n');
 
+       for (;;) {
+               if ((descr = reallocf(descr, descrlen)) != NULL) {
+                       ifr.ifr_buffer.buffer = descr;
+                       ifr.ifr_buffer.length = descrlen;
+                       if (ioctl(s, SIOCGIFDESCR, &ifr) == 0) {
+                               if (strlen(descr) > 0)
+                                       printf("\tdescription: %s\n", descr);
+                               break;
+                       } else if (errno == ENAMETOOLONG)
+                               descrlen = ifr.ifr_buffer.length;
+                       else
+                               break;
+               } else {
+                       warn("unable to allocate memory for interface"
+                           "description");
+                       break;
+               }
+       };
+
        if (ioctl(s, SIOCGIFCAP, (caddr_t)&ifr) == 0) {
                if (ifr.ifr_curcap != 0) {
                        printb("\toptions", ifr.ifr_curcap, IFCAPBITS);
@@ -1051,6 +1105,10 @@ static struct cmd basic_cmds[] = {
        DEF_CMD("-arp",         IFF_NOARP,      setifflags),
        DEF_CMD("debug",        IFF_DEBUG,      setifflags),
        DEF_CMD("-debug",       -IFF_DEBUG,     setifflags),
+       DEF_CMD_ARG("description",              setifdescr),
+       DEF_CMD_ARG("descr",                    setifdescr),
+       DEF_CMD("-description", 0,              unsetifdescr),
+       DEF_CMD("-descr",       0,              unsetifdescr),
        DEF_CMD("promisc",      IFF_PPROMISC,   setifflags),
        DEF_CMD("-promisc",     -IFF_PPROMISC,  setifflags),
        DEF_CMD("add",          IFF_UP,         notealias),
Index: share/man/man4/netintro.4
===================================================================
--- share/man/man4/netintro.4   (revision 203021)
+++ share/man/man4/netintro.4   (working copy)
@@ -32,7 +32,7 @@
 .\"     @(#)netintro.4 8.2 (Berkeley) 11/30/93
 .\" $FreeBSD$
 .\"
-.Dd June 18, 2004
+.Dd January 26, 2010
 .Dt NETINTRO 4
 .Os
 .Sh NAME
@@ -204,6 +204,7 @@ struct      ifreq {
         struct    sockaddr ifru_addr;
         struct    sockaddr ifru_dstaddr;
         struct    sockaddr ifru_broadaddr;
+        struct    ifreq_buffer ifru_buffer;
         short     ifru_flags[2];
         short     ifru_index;
         int       ifru_metric;
@@ -216,6 +217,7 @@ struct      ifreq {
 #define ifr_addr      ifr_ifru.ifru_addr      /* address */
 #define ifr_dstaddr   ifr_ifru.ifru_dstaddr   /* other end of p-to-p link */
 #define ifr_broadaddr ifr_ifru.ifru_broadaddr /* broadcast address */
+#define ifr_buffer    ifr_ifru.ifru_buffer    /* user supplied buffer with its 
length */
 #define ifr_flags     ifr_ifru.ifru_flags[0]  /* flags (low 16 bits) */
 #define ifr_flagshigh ifr_ifru.ifru_flags[1]  /* flags (high 16 bits) */
 #define ifr_metric    ifr_ifru.ifru_metric    /* metric */
@@ -277,6 +279,32 @@ and
 fields of the
 .Vt ifreq
 structure, respectively.
+.It Dv SIOCGIFDESCR
+Get the interface description, returned in the
+.Va buffer
+field of
+.Va ifru_buffer
+struct.
+The user supplied buffer length should be defined in the
+.Va length
+field of
+.Va ifru_buffer
+struct passed in as parameter, and the length would include
+the terminating nul character.  If there is not enough space
+to hold the interface length, no copy would be done and an
+error would be returned.  The kernel will store the buffer
+length in the
+.Va length
+field upon return, regardless whether the buffer itself is
+sufficient to hold the data.
+.It Dv SIOCSIFDESCR
+Set the interface description to the value of the
+.Va buffer
+field of
+.Va ifru_buffer
+struct, with
+.Va length
+field specifying its length (counting the terminating nul).
 .It Dv SIOCSIFFLAGS
 Set interface flags field.
 If the interface is marked down,
@@ -404,6 +432,13 @@ struct if_clonereq {
         char    *ifcr_buffer;   /* buffer for cloner names */
 };
 .Ed
+.Bd -literal
+/* Structure used in SIOCGIFDESCR and SIOCSIFDESCR requests */
+struct ifreq_buffer {
+        size_t  length;         /* length of the buffer */
+        void   *buffer;         /* pointer to userland space buffer */
+};
+.Ed
 .Sh SEE ALSO
 .Xr ioctl 2 ,
 .Xr socket 2 ,
Index: sys/kern/kern_jail.c
===================================================================
--- sys/kern/kern_jail.c        (revision 203021)
+++ sys/kern/kern_jail.c        (working copy)
@@ -3592,6 +3592,7 @@ prison_priv_check(struct ucred *cred, int priv)
        case PRIV_NET_SETIFMTU:
        case PRIV_NET_SETIFFLAGS:
        case PRIV_NET_SETIFCAP:
+       case PRIV_NET_SETIFDESCR:
        case PRIV_NET_SETIFNAME :
        case PRIV_NET_SETIFMETRIC:
        case PRIV_NET_SETIFPHYS:
Index: sys/net/if.c
===================================================================
--- sys/net/if.c        (revision 203021)
+++ sys/net/if.c        (working copy)
@@ -106,6 +106,18 @@ SYSCTL_INT(_net_link, OID_AUTO, log_link_state_cha
        &log_link_state_change, 0,
        "log interface link state change events");
 
+/* Interface description */
+static unsigned int ifdescr_maxlen = 1024;
+SYSCTL_UINT(_net, OID_AUTO, ifdescr_maxlen, CTLFLAG_RW,
+       &ifdescr_maxlen, 0,
+       "administrative maximum length for interface description");
+
+MALLOC_DEFINE(M_IFDESCR, "ifdescr", "ifnet descriptions");
+
+/* global sx for non-critical path ifdescr */
+static struct sx ifdescr_sx;
+SX_SYSINIT(ifdescr_sx, &ifdescr_sx, "ifnet descr");
+
 void   (*bstp_linkstate_p)(struct ifnet *ifp, int state);
 void   (*ng_ether_link_state_p)(struct ifnet *ifp, int state);
 void   (*lagg_linkstate_p)(struct ifnet *ifp, int state);
@@ -442,6 +454,8 @@ if_free_internal(struct ifnet *ifp)
 #ifdef MAC
        mac_ifnet_destroy(ifp);
 #endif /* MAC */
+       if (ifp->if_description != NULL)
+               free(ifp->if_description, M_IFDESCR);
        IF_AFDATA_DESTROY(ifp);
        IF_ADDR_LOCK_DESTROY(ifp);
        ifq_delete(&ifp->if_snd);
@@ -1979,6 +1993,8 @@ ifhwioctl(u_long cmd, struct ifnet *ifp, caddr_t d
        int error = 0;
        int new_flags, temp_flags;
        size_t namelen, onamelen;
+       size_t descrlen;
+       char *descrbuf, *odescrbuf;
        char new_name[IFNAMSIZ];
        struct ifaddr *ifa;
        struct sockaddr_dl *sdl;
@@ -2018,6 +2034,60 @@ ifhwioctl(u_long cmd, struct ifnet *ifp, caddr_t d
                ifr->ifr_phys = ifp->if_physical;
                break;
 
+       case SIOCGIFDESCR:
+               error = 0;
+               sx_slock(&ifdescr_sx);
+               if (ifp->if_description == NULL) {
+                       ifr->ifr_buffer.length = 0;
+                       error = ENOMSG;
+               } else {
+                       /* space for terminating nul */
+                       descrlen = strlen(ifp->if_description) + 1;
+                       if (ifr->ifr_buffer.length < descrlen)
+                               error = ENAMETOOLONG;
+                       else
+                               error = copyout(ifp->if_description,
+                                   ifr->ifr_buffer.buffer, descrlen);
+                       ifr->ifr_buffer.length = descrlen;
+               }
+               sx_sunlock(&ifdescr_sx);
+               break;
+
+       case SIOCSIFDESCR:
+               error = priv_check(td, PRIV_NET_SETIFDESCR);
+               if (error)
+                       return (error);
+
+               /*
+                * Copy only (length-1) bytes to make sure that
+                * if_description is always nul terminated.  The
+                * length parameter is supposed to count the
+                * terminating nul in.
+                */
+               if (ifr->ifr_buffer.length > ifdescr_maxlen)
+                       return (ENAMETOOLONG);
+               else if (ifr->ifr_buffer.length == 0)
+                       descrbuf = NULL;
+               else {
+                       descrbuf = malloc(ifr->ifr_buffer.length, M_IFDESCR,
+                           M_WAITOK | M_ZERO);
+                       error = copyin(ifr->ifr_buffer.buffer, descrbuf,
+                           ifr->ifr_buffer.length - 1);
+                       if (error) {
+                               free(descrbuf, M_IFDESCR);
+                               break;
+                       }
+               }
+
+               sx_xlock(&ifdescr_sx);
+               odescrbuf = ifp->if_description;
+               ifp->if_description = descrbuf;
+               sx_xunlock(&ifdescr_sx);
+
+               getmicrotime(&ifp->if_lastchange);
+               free(odescrbuf, M_IFDESCR);
+               break;
+
        case SIOCSIFFLAGS:
                error = priv_check(td, PRIV_NET_SETIFFLAGS);
                if (error)
Index: sys/net/if.h
===================================================================
--- sys/net/if.h        (revision 203021)
+++ sys/net/if.h        (working copy)
@@ -284,6 +284,14 @@ struct if_announcemsghdr {
 #define        IFAN_DEPARTURE  1       /* interface departure */
 
 /*
+ * Buffer with length to be used in SIOCGIFDESCR/SIOCSIFDESCR requests
+ */
+struct ifreq_buffer {
+       size_t  length;
+       void    *buffer;
+};
+
+/*
  * Interface request structure used for socket
  * ioctl's.  All interface ioctl's must have parameter
  * definitions which begin with ifr_name.  The
@@ -295,6 +303,7 @@ struct      ifreq {
                struct  sockaddr ifru_addr;
                struct  sockaddr ifru_dstaddr;
                struct  sockaddr ifru_broadaddr;
+               struct  ifreq_buffer ifru_buffer;
                short   ifru_flags[2];
                short   ifru_index;
                int     ifru_jid;
@@ -308,6 +317,7 @@ struct      ifreq {
 #define        ifr_addr        ifr_ifru.ifru_addr      /* address */
 #define        ifr_dstaddr     ifr_ifru.ifru_dstaddr   /* other end of p-to-p 
link */
 #define        ifr_broadaddr   ifr_ifru.ifru_broadaddr /* broadcast address */
+#define        ifr_buffer      ifr_ifru.ifru_buffer    /* user supplied buffer 
with its length */
 #define        ifr_flags       ifr_ifru.ifru_flags[0]  /* flags (low 16 bits) 
*/
 #define        ifr_flagshigh   ifr_ifru.ifru_flags[1]  /* flags (high 16 bits) 
*/
 #define        ifr_jid         ifr_ifru.ifru_jid       /* jail/vnet */
Index: sys/net/if_var.h
===================================================================
--- sys/net/if_var.h    (revision 203021)
+++ sys/net/if_var.h    (working copy)
@@ -203,7 +203,8 @@ struct ifnet {
         * be used with care where binary compatibility is required.
         */
        char     if_cspare[3];
-       void    *if_pspare[8];
+       char    *if_description;        /* interface description */
+       void    *if_pspare[7];
        int     if_ispare[4];
 };
 
Index: sys/sys/param.h
===================================================================
--- sys/sys/param.h     (revision 203021)
+++ sys/sys/param.h     (working copy)
@@ -58,7 +58,7 @@
  *             in the range 5 to 9.
  */
 #undef __FreeBSD_version
-#define __FreeBSD_version 900008       /* Master, propagated to newvers */
+#define __FreeBSD_version 900009       /* Master, propagated to newvers */
 
 #ifndef LOCORE
 #include <sys/types.h>
Index: sys/sys/priv.h
===================================================================
--- sys/sys/priv.h      (revision 203021)
+++ sys/sys/priv.h      (working copy)
@@ -335,6 +335,7 @@
 #define        PRIV_NET_LAGG           415     /* Administer lagg interface. */
 #define        PRIV_NET_GIF            416     /* Administer gif interface. */
 #define        PRIV_NET_SETIFVNET      417     /* Move interface to vnet. */
+#define        PRIV_NET_SETIFDESCR     418     /* Set interface description. */
 
 /*
  * 802.11-related privileges.
Index: sys/sys/sockio.h
===================================================================
--- sys/sys/sockio.h    (revision 203021)
+++ sys/sys/sockio.h    (working copy)
@@ -82,6 +82,8 @@
 #define        SIOCGIFMAC      _IOWR('i', 38, struct ifreq)    /* get IF MAC 
label */
 #define        SIOCSIFMAC       _IOW('i', 39, struct ifreq)    /* set IF MAC 
label */
 #define        SIOCSIFNAME      _IOW('i', 40, struct ifreq)    /* set IF name 
*/
+#define        SIOCSIFDESCR     _IOW('i', 41, struct ifreq)    /* set ifnet 
descr */ 
+#define        SIOCGIFDESCR    _IOWR('i', 42, struct ifreq)    /* get ifnet 
descr */ 
 
 #define        SIOCADDMULTI     _IOW('i', 49, struct ifreq)    /* add m'cast 
addr */
 #define        SIOCDELMULTI     _IOW('i', 50, struct ifreq)    /* del m'cast 
addr */
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