Date: Sun, 19 Apr 2020 16:19:06 +0200 From: "Kristof Provost" <kp@FreeBSD.org> To: "Ronald Klop" <ronald-lists@klop.ws> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r360068 - in head/sys: kern net sys Message-ID: <67B55A62-848B-4876-8367-DE0D32A8B7D4@FreeBSD.org> In-Reply-To: <op.0jbpatnnkndu52@sjakie> References: <202004180750.03I7oUK6032898@repo.freebsd.org> <op.0jbpatnnkndu52@sjakie>
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On 19 Apr 2020, at 15:33, Ronald Klop wrote: > On Sat, 18 Apr 2020 09:50:30 +0200, Kristof Provost <kp@freebsd.org> = > 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 >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D >> --- 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 >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D >> --- 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 =3D 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 =3D 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. > That would potentially be valuable, yes. On the other hand, we = traditionally don=E2=80=99t sprinkle a lot of printf()s around in the ker= nel. = This is extremely unlikely to happen, and if it does odds are attaching = the interface will fail at an earlier or later point, you may struggle = to pass packets and run into any number of other issues. It=E2=80=99s also possible to diagnose absent the printf(), because the M= AC = address will be locally administered rather than within the FreeBSD OUI. So, in short: not a bad idea. You can argue it both ways, and I find = myself (weakly) on the opposite side. Best regards, Kristof
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