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Improve MAC address uniqueness on if_epair(4).

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As reported in PR184149, it can happen that epair devices can have the same
MAC address.
This solution is based on a 32-bit hash, obtained combining the if_index of
the a interface and the hostid.
If the hostid is zero, a random number is used.

PR:		184149
Reviewed by:	wollman, eugen
Approved by:	cognet
Differential Revision:	https://reviews.freebsd.org/D15329
This commit is contained in:
Luca Pizzamiglio 2018-05-23 13:10:57 +00:00
parent d14732d366
commit 11d416666d
1 changed files with 24 additions and 8 deletions
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32
sys/net/if_epair.c
View File

@ -53,10 +53,14 @@
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/hash.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/libkern.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/module.h>
#include <sys/proc.h>
#include <sys/refcount.h>
#include <sys/queue.h>
#include <sys/smp.h>
@ -713,6 +717,9 @@ epair_clone_create(struct if_clone *ifc, char *name, size_t len, caddr_t params)
struct ifnet *ifp;
char *dp;
int error, unit, wildcard;
uint64_t hostid;
uint32_t key[3];
uint32_t hash;
uint8_t eaddr[ETHER_ADDR_LEN]; /* 00:00:00:00:00:00 */
/*
@ -724,14 +731,12 @@ epair_clone_create(struct if_clone *ifc, char *name, size_t len, caddr_t params)
if (params) {
scb = (struct epair_softc *)params;
ifp = scb->ifp;
/* Assign a hopefully unique, locally administered etheraddr. */
eaddr[0] = 0x02;
eaddr[3] = (ifp->if_index >> 8) & 0xff;
eaddr[4] = ifp->if_index & 0xff;
/* Copy epairNa etheraddr and change the last byte. */
memcpy(eaddr, scb->oifp->if_hw_addr, ETHER_ADDR_LEN);
eaddr[5] = 0x0b;
ether_ifattach(ifp, eaddr);
/* Correctly set the name for the cloner list. */
strlcpy(name, scb->ifp->if_xname, len);
strlcpy(name, ifp->if_xname, len);
return (0);
}
@ -835,10 +840,21 @@ epair_clone_create(struct if_clone *ifc, char *name, size_t len, caddr_t params)
ifp->if_init = epair_init;
if_setsendqlen(ifp, ifqmaxlen);
if_setsendqready(ifp);
/* Assign a hopefully unique, locally administered etheraddr. */
/*
* Calculate the etheraddr hashing the hostid and the
* interface index. The result would be hopefully unique
*/
getcredhostid(curthread->td_ucred, (unsigned long *)&hostid);
if (hostid == 0)
arc4rand(&hostid, sizeof(hostid), 0);
key[0] = (uint32_t)ifp->if_index;
key[1] = (uint32_t)(hostid & 0xffffffff);
key[2] = (uint32_t)((hostid >> 32) & 0xfffffffff);
hash = jenkins_hash32(key, 3, 0);
eaddr[0] = 0x02;
eaddr[3] = (ifp->if_index >> 8) & 0xff;
eaddr[4] = ifp->if_index & 0xff;
memcpy(&eaddr[1], &hash, 4);
eaddr[5] = 0x0a;
ether_ifattach(ifp, eaddr);
sca->if_qflush = ifp->if_qflush;