[PATCH] inet: support retrieving MAC address on BSD

[Michael Santos]

On systems supporting getaddrinfo(), support looking up the MAC
address from inet:ifget/2. The results have the same quirks as with
Linux: if the MAC address is longer than 6 bytes (e.g., fw0 under
Mac OS X), the address is truncated; if the interface does not have
a MAC address (e.g., lo0), an address consisting of 0's is returned.
---
 erts/configure.in                       |    3 ++
 erts/emulator/drivers/common/inet_drv.c |   40 +++++++++++++++++++++++++++---
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/erts/configure.in b/erts/configure.in
index 63bf548..74cb953 100644
--- a/erts/configure.in
+++ b/erts/configure.in
@@ -1764,6 +1764,9 @@ AC_CHECK_FUNCS([fdatasync])
 dnl Find which C libraries are required to use fdatasync
 AC_SEARCH_LIBS(fdatasync, [rt])
 
+AC_CHECK_HEADERS(net/if_dl.h ifaddrs.h)
+AC_CHECK_FUNCS([getifaddrs])
+
 dnl ----------------------------------------------------------------------
 dnl Checks for features/quirks in the system that affects Erlang.
 dnl ----------------------------------------------------------------------
diff --git a/erts/emulator/drivers/common/inet_drv.c b/erts/emulator/drivers/common/inet_drv.c
index 0ea5493..e55208f 100644
--- a/erts/emulator/drivers/common/inet_drv.c
+++ b/erts/emulator/drivers/common/inet_drv.c
@@ -48,6 +48,12 @@
 #include <sys/uio.h>
 #endif
 
+#ifdef HAVE_NET_IF_DL_H
+#include <net/if_dl.h>
+#endif
+#ifdef HAVE_IFADDRS_H
+#include <ifaddrs.h>
+#endif
 
 /* All platforms fail on malloc errors. */
 #define FATAL_MALLOC
@@ -4089,6 +4095,10 @@ static int inet_ctl_getiflist(inet_descriptor* desc, char** rbuf, int rsize)
 }
 
 
+/* FIXME: temporary hack */
+#ifndef IFHWADDRLEN
+#define IFHWADDRLEN 6
+#endif
 
 static int inet_ctl_ifget(inet_descriptor* desc, char* buf, int len,
 			  char** rbuf, int rsize)
@@ -4128,6 +4138,32 @@ static int inet_ctl_ifget(inet_descriptor* desc, char* buf, int len,
 	    /* raw memcpy (fix include autoconf later) */
 	    sys_memcpy(sptr, (char*)(&ifreq.ifr_hwaddr.sa_data), IFHWADDRLEN);
 	    sptr += IFHWADDRLEN;
+#elif defined(HAVE_GETIFADDRS)
+        struct ifaddrs *ifa, *ifp;
+        int found = 0;
+
+        if (getifaddrs(&ifa) == -1)
+        goto error;
+
+        for (ifp = ifa; ifp; ifp = ifp->ifa_next) {
+        if ((ifp->ifa_addr->sa_family == AF_LINK) &&
+        (sys_strcmp(ifp->ifa_name, ifreq.ifr_name) == 0)) {
+            found = 1;
+            break;
+        }
+        }
+
+        if (found == 0) {
+            freeifaddrs(ifa);
+            break;
+        }
+
+        buf_check(sptr, s_end, 1+IFHWADDRLEN);
+        *sptr++ = INET_IFOPT_HWADDR;
+        sys_memcpy(sptr, ((struct sockaddr_dl *)ifp->ifa_addr)->sdl_data +
+            ((struct sockaddr_dl *)ifp->ifa_addr)->sdl_nlen, IFHWADDRLEN);
+        freeifaddrs(ifa);
+        sptr += IFHWADDRLEN;
 #endif
 	    break;
 	}
@@ -4240,10 +4276,6 @@ static int inet_ctl_ifget(inet_descriptor* desc, char* buf, int len,
     return ctl_error(EINVAL, rbuf, rsize);
 }
 
-/* FIXME: temporary hack */
-#ifndef IFHWADDRLEN
-#define IFHWADDRLEN 6
-#endif
 
 static int inet_ctl_ifset(inet_descriptor* desc, char* buf, int len,
 			  char** rbuf, int rsize)
-- 
1.5.6.4