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[lltable] Restructure nd6 code.

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Factor out lltable locking logic from lltable_try_set_entry_addr()
 into a separate lltable_acquire_wlock(), so the latter can be used
 in other parts of the code w/o duplication.

Create nd6_try_set_entry_addr() to avoid code duplication in nd6.c
 and nd6_nbr.c.

Move lle creation logic from nd6_resolve_slow() into a separate
 nd6_get_llentry() to simplify the former.

These changes serve as a pre-requisite for implementing
 RFC8950 (IPv4 prefixes with IPv6 nexthops).

Differential Revision: https://reviews.freebsd.org/D31432
MFC after:	2 weeks
This commit is contained in:
Alexander V. Chernikov 2021-08-06 08:27:22 +00:00
parent 3676512b60
commit 0b79b007eb
5 changed files with 109 additions and 67 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
sys/net/if_llatbl.c
View File

@ -317,6 +317,35 @@ lltable_set_entry_addr(struct ifnet *ifp, struct llentry *lle,
lle->r_flags |= RLLE_VALID;
}
/*
* Acquires lltable write lock.
*
* Returns true on success, with both lltable and lle lock held.
* On failure, false is returned and lle wlock is still held.
*/
bool
lltable_acquire_wlock(struct ifnet *ifp, struct llentry *lle)
{
NET_EPOCH_ASSERT();
/* Perform real LLE update */
/* use afdata WLOCK to update fields */
LLE_WUNLOCK(lle);
IF_AFDATA_WLOCK(ifp);
LLE_WLOCK(lle);
/*
* Since we droppped LLE lock, other thread might have deleted
* this lle. Check and return
*/
if ((lle->la_flags & LLE_DELETED) != 0) {
IF_AFDATA_WUNLOCK(ifp);
return (false);
}
return (true);
}
/*
* Tries to update @lle link-level address.
* Since update requires AFDATA WLOCK, function
@ -330,31 +359,14 @@ lltable_try_set_entry_addr(struct ifnet *ifp, struct llentry *lle,
const char *linkhdr, size_t linkhdrsize, int lladdr_off)
{
/* Perform real LLE update */
/* use afdata WLOCK to update fields */
LLE_WLOCK_ASSERT(lle);
LLE_ADDREF(lle);
LLE_WUNLOCK(lle);
IF_AFDATA_WLOCK(ifp);
LLE_WLOCK(lle);
/*
* Since we droppped LLE lock, other thread might have deleted
* this lle. Check and return
*/
if ((lle->la_flags & LLE_DELETED) != 0) {
IF_AFDATA_WUNLOCK(ifp);
LLE_FREE_LOCKED(lle);
if (!lltable_acquire_wlock(ifp, lle))
return (0);
}
/* Update data */
lltable_set_entry_addr(ifp, lle, linkhdr, linkhdrsize, lladdr_off);
IF_AFDATA_WUNLOCK(ifp);
LLE_REMREF(lle);
return (1);
}

2
sys/net/if_llatbl.h
View File

@ -238,6 +238,8 @@ void lltable_fill_sa_entry(const struct llentry *lle, struct sockaddr *sa);
struct ifnet *lltable_get_ifp(const struct lltable *llt);
int lltable_get_af(const struct lltable *llt);
bool lltable_acquire_wlock(struct ifnet *ifp, struct llentry *lle);
int lltable_foreach_lle(struct lltable *llt, llt_foreach_cb_t *f,
void *farg);
/*

114
sys/netinet6/nd6.c
View File

@ -1382,6 +1382,35 @@ nd6_is_addr_neighbor(const struct sockaddr_in6 *addr, struct ifnet *ifp)
return (rc);
}
/*
* Tries to update @lle address/prepend data with new @lladdr.
*
* Returns true on success.
* In any case, @lle is returned wlocked.
*/
bool
nd6_try_set_entry_addr(struct ifnet *ifp, struct llentry *lle, char *lladdr)
{
u_char linkhdr[LLE_MAX_LINKHDR];
size_t linkhdrsize;
int lladdr_off;
LLE_WLOCK_ASSERT(lle);
linkhdrsize = sizeof(linkhdr);
if (lltable_calc_llheader(ifp, AF_INET6, lladdr,
linkhdr, &linkhdrsize, &lladdr_off) != 0) {
return (false);
}
if (!lltable_acquire_wlock(ifp, lle))
return (false);
lltable_set_entry_addr(ifp, lle, linkhdr, linkhdrsize, lladdr_off);
IF_AFDATA_WUNLOCK(ifp);
return (true);
}
/*
* Free an nd6 llinfo entry.
* Since the function would cause significant changes in the kernel, DO NOT
@ -2027,14 +2056,9 @@ nd6_cache_lladdr(struct ifnet *ifp, struct in6_addr *from, char *lladdr,
* Record source link-layer address
* XXX is it dependent to ifp->if_type?
*/
linkhdrsize = sizeof(linkhdr);
if (lltable_calc_llheader(ifp, AF_INET6, lladdr,
linkhdr, &linkhdrsize, &lladdr_off) != 0)
return;
if (lltable_try_set_entry_addr(ifp, ln, linkhdr, linkhdrsize,
lladdr_off) == 0) {
if (!nd6_try_set_entry_addr(ifp, ln, lladdr)) {
/* Entry was deleted */
LLE_WUNLOCK(ln);
return;
}
@ -2257,6 +2281,39 @@ nd6_resolve(struct ifnet *ifp, int is_gw, struct mbuf *m,
return (nd6_resolve_slow(ifp, 0, m, dst6, desten, pflags, plle));
}
/*
* Finds or creates a new llentry for @addr.
* Returns wlocked llentry or NULL.
*/
static __noinline struct llentry *
nd6_get_llentry(struct ifnet *ifp, const struct in6_addr *addr)
{
struct llentry *lle, *lle_tmp;
lle = nd6_alloc(addr, 0, ifp);
if (lle == NULL) {
char ip6buf[INET6_ADDRSTRLEN];
log(LOG_DEBUG,
"nd6_get_llentry: can't allocate llinfo for %s "
"(ln=%p)\n",
ip6_sprintf(ip6buf, addr), lle);
return (NULL);
}
IF_AFDATA_WLOCK(ifp);
LLE_WLOCK(lle);
/* Prefer any existing entry over newly-created one */
lle_tmp = nd6_lookup(addr, LLE_EXCLUSIVE, ifp);
if (lle_tmp == NULL)
lltable_link_entry(LLTABLE6(ifp), lle);
IF_AFDATA_WUNLOCK(ifp);
if (lle_tmp != NULL) {
lltable_free_entry(LLTABLE6(ifp), lle);
return (lle_tmp);
} else
return (lle);
}
/*
* Do L2 address resolution for @sa_dst address. Stores found
* address in @desten buffer. Copy of lle ln_flags can be also
@ -2273,7 +2330,7 @@ nd6_resolve_slow(struct ifnet *ifp, int flags, struct mbuf *m,
const struct sockaddr_in6 *dst, u_char *desten, uint32_t *pflags,
struct llentry **plle)
{
struct llentry *lle = NULL, *lle_tmp;
struct llentry *lle = NULL;
struct in6_addr *psrc, src;
int send_ns, ll_len;
char *lladdr;
@ -2286,39 +2343,16 @@ nd6_resolve_slow(struct ifnet *ifp, int flags, struct mbuf *m,
* At this point, the destination of the packet must be a unicast
* or an anycast address(i.e. not a multicast).
*/
if (lle == NULL) {
lle = nd6_lookup(&dst->sin6_addr, LLE_EXCLUSIVE, ifp);
if ((lle == NULL) && nd6_is_addr_neighbor(dst, ifp)) {
/*
* Since nd6_is_addr_neighbor() internally calls nd6_lookup(),
* the condition below is not very efficient. But we believe
* it is tolerable, because this should be a rare case.
*/
lle = nd6_alloc(&dst->sin6_addr, 0, ifp);
if (lle == NULL) {
char ip6buf[INET6_ADDRSTRLEN];
log(LOG_DEBUG,
"nd6_output: can't allocate llinfo for %s "
"(ln=%p)\n",
ip6_sprintf(ip6buf, &dst->sin6_addr), lle);
m_freem(m);
return (ENOBUFS);
}
lle = nd6_lookup(&dst->sin6_addr, LLE_EXCLUSIVE, ifp);
if ((lle == NULL) && nd6_is_addr_neighbor(dst, ifp)) {
/*
* Since nd6_is_addr_neighbor() internally calls nd6_lookup(),
* the condition below is not very efficient. But we believe
* it is tolerable, because this should be a rare case.
*/
lle = nd6_get_llentry(ifp, &dst->sin6_addr);
}
IF_AFDATA_WLOCK(ifp);
LLE_WLOCK(lle);
/* Prefer any existing entry over newly-created one */
lle_tmp = nd6_lookup(&dst->sin6_addr, LLE_EXCLUSIVE, ifp);
if (lle_tmp == NULL)
lltable_link_entry(LLTABLE6(ifp), lle);
IF_AFDATA_WUNLOCK(ifp);
if (lle_tmp != NULL) {
lltable_free_entry(LLTABLE6(ifp), lle);
lle = lle_tmp;
lle_tmp = NULL;
}
}
}
if (lle == NULL) {
m_freem(m);
return (ENOBUFS);

1
sys/netinet6/nd6.h
View File

@ -376,6 +376,7 @@ int nd6_resolve(struct ifnet *, int, struct mbuf *,
int nd6_ioctl(u_long, caddr_t, struct ifnet *);
void nd6_cache_lladdr(struct ifnet *, struct in6_addr *,
char *, int, int, int);
bool nd6_try_set_entry_addr(struct ifnet *ifp, struct llentry *lle, char *lladdr);
struct mbuf *nd6_grab_holdchain(struct llentry *);
int nd6_flush_holdchain(struct ifnet *, struct llentry *, struct mbuf *);
int nd6_add_ifa_lle(struct in6_ifaddr *);

11
sys/netinet6/nd6_nbr.c
View File

@ -770,16 +770,9 @@ nd6_na_input(struct mbuf *m, int off, int icmp6len)
/*
* Record link-layer address, and update the state.
*/
linkhdrsize = sizeof(linkhdr);
if (lltable_calc_llheader(ifp, AF_INET6, lladdr,
linkhdr, &linkhdrsize, &lladdr_off) != 0)
return;
if (lltable_try_set_entry_addr(ifp, ln, linkhdr, linkhdrsize,
lladdr_off) == 0) {
ln = NULL;
if (!nd6_try_set_entry_addr(ifp, ln, lladdr))
goto freeit;
}
EVENTHANDLER_INVOKE(lle_event, ln, LLENTRY_RESOLVED);
if (is_solicited)
nd6_llinfo_setstate(ln, ND6_LLINFO_REACHABLE);