Hi,
Wouldn't it be user friendly to tell why the MAC is random? Something like this.
if (strncmp(uuid, DEFAULT_HOSTUUID, sizeof(uuid)) == 0) {
printf("No /etc/hostuuid found. Fall back to a random mac address.");
goto rando;
}
I know it would save me a lot of time if I would encounter this case.
Plus the message is only printed once on boot.
Regards,
Ronald.
Van: Kyle Evans <[email protected]>
Datum: woensdag, 2 juni 2021 05:59
Aan: [email protected], [email protected],
[email protected]
Onderwerp: git: 2d741f33bd07 - main - kern: ether_gen_addr: randomize on
default hostuuid, too
The branch main has been updated by kevans:
URL:
https://cgit.FreeBSD.org/src/commit/?id=2d741f33bd07bf94a59635db3c7b9e070a8a6e55
commit 2d741f33bd07bf94a59635db3c7b9e070a8a6e55
Author: Kyle Evans <[email protected]>
AuthorDate: 2021-04-16 01:11:35 +0000
Commit: Kyle Evans <[email protected]>
CommitDate: 2021-06-02 03:59:21 +0000
kern: ether_gen_addr: randomize on default hostuuid, too
Currently, this will still hash the default (all zero) hostuuid and
potentially arrive at a MAC address that has a high chance of collision
if another interface of the same name appears in the same broadcast
domain on another host without a hostuuid, e.g., some virtual machine
setups.
Instead of using the default hostuuid, just treat it as a failure and
generate a random LA unicast MAC address.
Reviewed by: bz, gbe, imp, kbowling, kp
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D29788
---
share/man/man9/ether_gen_addr.9 | 5 +++--
sys/kern/kern_jail.c | 1 -
sys/net/if_ethersubr.c | 17 ++++++++++++++---
sys/sys/jail.h | 1 +
4 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/share/man/man9/ether_gen_addr.9 b/share/man/man9/ether_gen_addr.9
index 1b98a841736d..f69cb199e2c3 100644
--- a/share/man/man9/ether_gen_addr.9
+++ b/share/man/man9/ether_gen_addr.9
@@ -61,8 +61,9 @@ or on machines that do not use
.Xr loader 8 .
.Pp
.Nm
-can fail to derive a MAC address due to memory allocation failure.
-In this case, a locally-administered unicast MAC address will be randomly
+can fail to derive a MAC address due to memory allocation failure, or because
+the hostid has not been populated.
+In these cases, a locally-administered unicast MAC address will be randomly
generated and returned via the
.Ar hwaddr
parameter.
diff --git a/sys/kern/kern_jail.c b/sys/kern/kern_jail.c
index 303e31490eb1..9784f3bfc23b 100644
--- a/sys/kern/kern_jail.c
+++ b/sys/kern/kern_jail.c
@@ -76,7 +76,6 @@ __FBSDID("$FreeBSD$");
#include <security/mac/mac_framework.h>
-#define DEFAULT_HOSTUUID "00000000-0000-0000-0000-000000000000"
#define PRISON0_HOSTUUID_MODULE "hostuuid"
MALLOC_DEFINE(M_PRISON, "prison", "Prison structures");
diff --git a/sys/net/if_ethersubr.c b/sys/net/if_ethersubr.c
index 01c2d2f7b3e8..7eb46df8281a 100644
--- a/sys/net/if_ethersubr.c
+++ b/sys/net/if_ethersubr.c
@@ -1443,6 +1443,11 @@ ether_gen_addr(struct ifnet *ifp, struct ether_addr
*hwaddr)
char jailname[MAXHOSTNAMELEN];
getcredhostuuid(curthread->td_ucred, uuid, sizeof(uuid));
+ if (strncmp(uuid, DEFAULT_HOSTUUID, sizeof(uuid)) == 0) {
+ /* Fall back to a random mac address. */
+ goto rando;
+ }
+
/* If each (vnet) jail would also have a unique hostuuid this would not
* be necessary. */
getjailname(curthread->td_ucred, jailname, sizeof(jailname));
@@ -1450,9 +1455,7 @@ ether_gen_addr(struct ifnet *ifp, struct ether_addr
*hwaddr)
jailname);
if (sz < 0) {
/* Fall back to a random mac address. */
- arc4rand(hwaddr, sizeof(*hwaddr), 0);
- hwaddr->octet[0] = 0x02;
- return;
+ goto rando;
}
SHA1Init(&ctx);
@@ -1467,6 +1470,14 @@ ether_gen_addr(struct ifnet *ifp, struct ether_addr
*hwaddr)
hwaddr->octet[i] = addr >> ((ETHER_ADDR_LEN - i - 1) * 8) &
0xFF;
}
+
+ return;
+rando:
+ arc4rand(hwaddr, sizeof(*hwaddr), 0);
+ /* Unicast */
+ hwaddr->octet[0] &= 0xFE;
+ /* Locally administered. */
+ hwaddr->octet[0] |= 0x02;
}
DECLARE_MODULE(ether, ether_mod, SI_SUB_INIT_IF, SI_ORDER_ANY);
diff --git a/sys/sys/jail.h b/sys/sys/jail.h
index c9d4c65e4d9e..76ed377e3f06 100644
--- a/sys/sys/jail.h
+++ b/sys/sys/jail.h
@@ -140,6 +140,7 @@ MALLOC_DECLARE(M_PRISON);
#include <sys/osd.h>
#define HOSTUUIDLEN 64
+#define DEFAULT_HOSTUUID "00000000-0000-0000-0000-000000000000"
#define OSRELEASELEN 32
struct racct;
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