Nice feature. A question below.
On Sat, 18 Apr 2020 09:50:30 +0200, Kristof Provost <[email protected]> wrote:
Author: kp
Date: Sat Apr 18 07:50:30 2020
New Revision: 360068
URL: https://svnweb.freebsd.org/changeset/base/360068
Log:
ethersubr: Make the mac address generation more robust
If we create two (vnet) jails and create a bridge interface in each we
end up
with the same mac address on both bridge interfaces.
These very often conflicts, resulting in same mac address in both
jails.
Mitigate this problem by including the jail name in the mac address.
Reviewed by: kevans, melifaro
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D24383
Modified:
head/sys/kern/kern_jail.c
head/sys/net/if_ethersubr.c
head/sys/sys/jail.h
Modified: head/sys/kern/kern_jail.c
==============================================================================
--- head/sys/kern/kern_jail.c Sat Apr 18 03:14:16 2020 (r360067)
+++ head/sys/kern/kern_jail.c Sat Apr 18 07:50:30 2020 (r360068)
@@ -2920,6 +2920,15 @@ getcredhostid(struct ucred *cred, unsigned long
*hosti
mtx_unlock(&cred->cr_prison->pr_mtx);
}
+void
+getjailname(struct ucred *cred, char *name, size_t len)
+{
+
+ mtx_lock(&cred->cr_prison->pr_mtx);
+ strlcpy(name, cred->cr_prison->pr_name, len);
+ mtx_unlock(&cred->cr_prison->pr_mtx);
+}
+
#ifdef VIMAGE
/*
* Determine whether the prison represented by cred owns
Modified: head/sys/net/if_ethersubr.c
==============================================================================
--- head/sys/net/if_ethersubr.c Sat Apr 18 03:14:16 2020 (r360067)
+++ head/sys/net/if_ethersubr.c Sat Apr 18 07:50:30 2020 (r360068)
@@ -1419,27 +1419,39 @@ ether_8021q_frame(struct mbuf **mp, struct ifnet
*ife,
/*
* Allocate an address from the FreeBSD Foundation OUI. This uses a
- * cryptographic hash function on the containing jail's UUID and the
interface
- * name to attempt to provide a unique but stable address.
Pseudo-interfaces
- * which require a MAC address should use this function to allocate
- * non-locally-administered addresses.
+ * cryptographic hash function on the containing jail's name, UUID and
the
+ * interface name to attempt to provide a unique but stable address.
+ * Pseudo-interfaces which require a MAC address should use this
function to
+ * allocate non-locally-administered addresses.
*/
void
ether_gen_addr(struct ifnet *ifp, struct ether_addr *hwaddr)
{
-#define ETHER_GEN_ADDR_BUFSIZ HOSTUUIDLEN + IFNAMSIZ + 2
SHA1_CTX ctx;
- char buf[ETHER_GEN_ADDR_BUFSIZ];
+ char *buf;
char uuid[HOSTUUIDLEN + 1];
uint64_t addr;
int i, sz;
char digest[SHA1_RESULTLEN];
+ char jailname[MAXHOSTNAMELEN];
getcredhostuuid(curthread->td_ucred, uuid, sizeof(uuid));
- sz = snprintf(buf, ETHER_GEN_ADDR_BUFSIZ, "%s-%s", uuid,
ifp->if_xname);
+ /* If each (vnet) jail would also have a unique hostuuid this would not
+ * be necessary. */
+ getjailname(curthread->td_ucred, jailname, sizeof(jailname));
+ sz = asprintf(&buf, M_TEMP, "%s-%s-%s", uuid, if_name(ifp),
+ jailname);
+ if (sz < 0) {
+ /* Fall back to a random mac address. */
I was wondering if it would be valuable to give this fall back something
like:
printf("%s: unable to create fixed mac address; using random
mac address", if_name(ifp));
This will only be printed in rare circumstances. But in that case will
provide valuable information.
Regards,
Ronald.
+ arc4rand(hwaddr, sizeof(*hwaddr), 0);
+ hwaddr->octet[0] = 0x02;
+ return;
+ }
+
SHA1Init(&ctx);
SHA1Update(&ctx, buf, sz);
SHA1Final(digest, &ctx);
+ free(buf, M_TEMP);
addr = ((digest[0] << 16) | (digest[1] << 8) | digest[2]) &
OUI_FREEBSD_GENERATED_MASK;
Modified: head/sys/sys/jail.h
==============================================================================
--- head/sys/sys/jail.h Sat Apr 18 03:14:16 2020 (r360067)
+++ head/sys/sys/jail.h Sat Apr 18 07:50:30 2020 (r360068)
@@ -382,6 +382,7 @@ void getcredhostname(struct ucred *, char *, size_t);
void getcreddomainname(struct ucred *, char *, size_t);
void getcredhostuuid(struct ucred *, char *, size_t);
void getcredhostid(struct ucred *, unsigned long *);
+void getjailname(struct ucred *cred, char *name, size_t len);
void prison0_init(void);
int prison_allow(struct ucred *, unsigned);
int prison_check(struct ucred *cred1, struct ucred *cred2);
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