Improve the distribution of LAGG port traffic.
I edited the original change to retain the use of arc4random() as a seed for the hashing as a very basic defense against intentional lagg port selection. The author's original commit message (edited slightly): sys/net/ieee8023ad_lacp.c sys/net/if_lagg.c In lagg_hashmbuf, use the FNV hash instead of the old hash32_buf. The hash32 family of functions operate one octet at a time, and when run on a string s of length n, their output is equivalent to : ----- i=n-1 \ n \ (n-i-1) 32 ( seed^ + / 33^ * s[i] ) % 2^ / ----- i=0 The problem is that the last five bytes of input don't get multiplied by sufficiently many powers of 33 to rollover 2^32. That means that changing the last few bytes (but obviously not the very last) of input will always change the value of the hash by a multiple of 33. In the case of lagg_hashmbuf() with ipv4 input, the last four bytes are the TCP or UDP port numbers. Since the output of lagg_hashmbuf is always taken modulo the port count, and 3 is a common port count for a lagg, that's bad. It means that the UDP or TCP source port will never affect which lagg member is selected on a 3-port lagg. At 10Gbps, I was not able to measure any difference in CPU consumption between the old and new hash. Submitted by: asomers (original commit) Reviewed by: emaste, glebius MFC after: 1 week Sponsored by: Spectra Logic MFSpectraBSD: 1001723 on 2013/08/28 (original) 1114258 on 2015/01/22 (edit)
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svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=277544
@ -35,6 +35,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/eventhandler.h>
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#include <sys/mbuf.h>
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#include <sys/systm.h>
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#include <sys/fnv_hash.h>
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#include <sys/malloc.h>
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#include <sys/kernel.h> /* hz */
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#include <sys/socket.h> /* for net/if.h */
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@ -757,13 +758,16 @@ void
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lacp_attach(struct lagg_softc *sc)
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{
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struct lacp_softc *lsc;
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uint32_t seed;
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lsc = malloc(sizeof(struct lacp_softc), M_DEVBUF, M_WAITOK | M_ZERO);
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sc->sc_psc = lsc;
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lsc->lsc_softc = sc;
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lsc->lsc_hashkey = arc4random();
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seed = arc4random();
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lsc->lsc_hashkey = FNV1_32_INIT;
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lsc->lsc_hashkey = fnv_32_buf(&seed, sizeof(seed), lsc->lsc_hashkey);
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lsc->lsc_active_aggregator = NULL;
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lsc->lsc_strict_mode = 1;
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LACP_LOCK_INIT(lsc);
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@ -36,7 +36,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/priv.h>
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#include <sys/systm.h>
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#include <sys/proc.h>
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#include <sys/hash.h>
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#include <sys/fnv_hash.h>
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#include <sys/lock.h>
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#include <sys/rmlock.h>
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#include <sys/taskqueue.h>
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@ -1853,13 +1853,13 @@ lagg_hashmbuf(struct lagg_softc *sc, struct mbuf *m, uint32_t key)
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eh = mtod(m, struct ether_header *);
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etype = ntohs(eh->ether_type);
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if (sc->sc_flags & LAGG_F_HASHL2) {
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p = hash32_buf(&eh->ether_shost, ETHER_ADDR_LEN, p);
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p = hash32_buf(&eh->ether_dhost, ETHER_ADDR_LEN, p);
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p = fnv_32_buf(&eh->ether_shost, ETHER_ADDR_LEN, p);
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p = fnv_32_buf(&eh->ether_dhost, ETHER_ADDR_LEN, p);
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}
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/* Special handling for encapsulating VLAN frames */
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if ((m->m_flags & M_VLANTAG) && (sc->sc_flags & LAGG_F_HASHL2)) {
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p = hash32_buf(&m->m_pkthdr.ether_vtag,
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p = fnv_32_buf(&m->m_pkthdr.ether_vtag,
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sizeof(m->m_pkthdr.ether_vtag), p);
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} else if (etype == ETHERTYPE_VLAN) {
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vlan = lagg_gethdr(m, off, sizeof(*vlan), &buf);
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@ -1867,7 +1867,7 @@ lagg_hashmbuf(struct lagg_softc *sc, struct mbuf *m, uint32_t key)
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goto out;
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if (sc->sc_flags & LAGG_F_HASHL2)
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p = hash32_buf(&vlan->evl_tag, sizeof(vlan->evl_tag), p);
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p = fnv_32_buf(&vlan->evl_tag, sizeof(vlan->evl_tag), p);
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etype = ntohs(vlan->evl_proto);
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off += sizeof(*vlan) - sizeof(*eh);
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}
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@ -1880,8 +1880,8 @@ lagg_hashmbuf(struct lagg_softc *sc, struct mbuf *m, uint32_t key)
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goto out;
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if (sc->sc_flags & LAGG_F_HASHL3) {
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p = hash32_buf(&ip->ip_src, sizeof(struct in_addr), p);
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p = hash32_buf(&ip->ip_dst, sizeof(struct in_addr), p);
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p = fnv_32_buf(&ip->ip_src, sizeof(struct in_addr), p);
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p = fnv_32_buf(&ip->ip_dst, sizeof(struct in_addr), p);
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}
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if (!(sc->sc_flags & LAGG_F_HASHL4))
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break;
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@ -1896,7 +1896,7 @@ lagg_hashmbuf(struct lagg_softc *sc, struct mbuf *m, uint32_t key)
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ports = lagg_gethdr(m, off, sizeof(*ports), &buf);
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if (ports == NULL)
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break;
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p = hash32_buf(ports, sizeof(*ports), p);
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p = fnv_32_buf(ports, sizeof(*ports), p);
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break;
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}
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break;
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@ -1909,10 +1909,10 @@ lagg_hashmbuf(struct lagg_softc *sc, struct mbuf *m, uint32_t key)
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if (ip6 == NULL)
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goto out;
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p = hash32_buf(&ip6->ip6_src, sizeof(struct in6_addr), p);
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p = hash32_buf(&ip6->ip6_dst, sizeof(struct in6_addr), p);
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p = fnv_32_buf(&ip6->ip6_src, sizeof(struct in6_addr), p);
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p = fnv_32_buf(&ip6->ip6_dst, sizeof(struct in6_addr), p);
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flow = ip6->ip6_flow & IPV6_FLOWLABEL_MASK;
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p = hash32_buf(&flow, sizeof(flow), p); /* IPv6 flow label */
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p = fnv_32_buf(&flow, sizeof(flow), p); /* IPv6 flow label */
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break;
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#endif
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}
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@ -2087,12 +2087,15 @@ lagg_lb_attach(struct lagg_softc *sc)
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{
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struct lagg_port *lp;
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struct lagg_lb *lb;
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uint32_t seed;
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lb = malloc(sizeof(struct lagg_lb), M_DEVBUF, M_WAITOK | M_ZERO);
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sc->sc_capabilities = IFCAP_LAGG_FULLDUPLEX;
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lb->lb_key = arc4random();
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seed = arc4random();
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lb->lb_key = FNV1_32_INIT;
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lb->lb_key = fnv_32_buf(&seed, sizeof(seed), lb->lb_key);
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sc->sc_psc = lb;
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SLIST_FOREACH(lp, &sc->sc_ports, lp_entries)
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