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ifnet/mbuf: provide KPI to serialize/restore m->m_pkthdr.rcvif

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Supplement ifindex table with generation count and use it to
serialize & restore an ifnet pointer.

Reviewed by:		kp
Differential revision:	https://reviews.freebsd.org/D33266
Fun note:		git show e6abef0918

(cherry picked from commit e1882428dc)
This commit is contained in:
Gleb Smirnoff 2022-01-26 21:58:50 -08:00 committed by Ed Maste
parent 80e60e236d
commit 4d7a1361ef
4 changed files with 72 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
sys/kern/kern_mbuf.c
View File

@ -1635,6 +1635,28 @@ m_snd_tag_destroy(struct m_snd_tag *mst)
counter_u64_add(snd_tag_count, -1);
}
void
m_rcvif_serialize(struct mbuf *m)
{
u_short idx, gen;
M_ASSERTPKTHDR(m);
idx = m->m_pkthdr.rcvif->if_index;
gen = m->m_pkthdr.rcvif->if_idxgen;
m->m_pkthdr.rcvidx = idx;
m->m_pkthdr.rcvgen = gen;
}
struct ifnet *
m_rcvif_restore(struct mbuf *m)
{
M_ASSERTPKTHDR(m);
return ((m->m_pkthdr.rcvif = ifnet_byindexgen(m->m_pkthdr.rcvidx,
m->m_pkthdr.rcvgen)));
}
/*
* Allocate an mbuf with anonymous external pages.
*/

49
sys/net/if.c
View File

@ -313,7 +313,10 @@ VNET_DEFINE(struct ifgrouphead, ifg_head);
/* Table of ifnet by index. */
static int if_index;
static int if_indexlim = 8;
static struct ifnet **ifindex_table;
static struct ifindex_entry {
struct ifnet *ife_ifnet;
uint16_t ife_gencnt;
} *ifindex_table;
SYSCTL_NODE(_net_link_generic, IFMIB_SYSTEM, system,
CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
@ -325,8 +328,8 @@ sysctl_ifcount(SYSCTL_HANDLER_ARGS)
IFNET_RLOCK();
for (int i = 1; i <= if_index; i++)
if (ifindex_table[i] != NULL &&
ifindex_table[i]->if_vnet == curvnet)
if (ifindex_table[i].ife_ifnet != NULL &&
ifindex_table[i].ife_ifnet->if_vnet == curvnet)
rv = i;
IFNET_RUNLOCK();
@ -370,7 +373,7 @@ ifnet_byindex(u_int idx)
if (__predict_false(idx > if_index))
return (NULL);
ifp = ck_pr_load_ptr(&ifindex_table[idx]);
ifp = ck_pr_load_ptr(&ifindex_table[idx].ife_ifnet);
if (curvnet != NULL && ifp != NULL && ifp->if_vnet != curvnet)
ifp = NULL;
@ -391,6 +394,24 @@ ifnet_byindex_ref(u_int idx)
return (ifp);
}
struct ifnet *
ifnet_byindexgen(uint16_t idx, uint16_t gen)
{
struct ifnet *ifp;
NET_EPOCH_ASSERT();
if (__predict_false(idx > if_index))
return (NULL);
ifp = ck_pr_load_ptr(&ifindex_table[idx].ife_ifnet);
if (ifindex_table[idx].ife_gencnt == gen)
return (ifp);
else
return (NULL);
}
/*
* Network interface utility routines.
*
@ -557,13 +578,13 @@ if_alloc_domain(u_char type, int numa_domain)
* next slot.
*/
for (idx = 1; idx <= if_index; idx++) {
if (ifindex_table[idx] == NULL)
if (ifindex_table[idx].ife_ifnet == NULL)
break;
}
/* Catch if_index overflow. */
if (idx >= if_indexlim) {
struct ifnet **new, **old;
struct ifindex_entry *new, *old;
int newlim;
newlim = if_indexlim * 2;
@ -579,7 +600,8 @@ if_alloc_domain(u_char type, int numa_domain)
if_index = idx;
ifp->if_index = idx;
ck_pr_store_ptr(&ifindex_table[idx], ifp);
ifp->if_idxgen = ifindex_table[idx].ife_gencnt;
ck_pr_store_ptr(&ifindex_table[idx].ife_ifnet, ifp);
IFNET_WUNLOCK();
return (ifp);
@ -654,9 +676,10 @@ if_free(struct ifnet *ifp)
* virtualized and interface would outlive the vnet.
*/
IFNET_WLOCK();
MPASS(ifindex_table[ifp->if_index] == ifp);
ck_pr_store_ptr(&ifindex_table[ifp->if_index], NULL);
while (if_index > 0 && ifindex_table[if_index] == NULL)
MPASS(ifindex_table[ifp->if_index].ife_ifnet == ifp);
ck_pr_store_ptr(&ifindex_table[ifp->if_index].ife_ifnet, NULL);
ifindex_table[ifp->if_index].ife_gencnt++;
while (if_index > 0 && ifindex_table[if_index].ife_ifnet == NULL)
if_index--;
IFNET_WUNLOCK();
@ -805,7 +828,7 @@ if_attach_internal(struct ifnet *ifp, bool vmove)
struct sockaddr_dl *sdl;
struct ifaddr *ifa;
MPASS(ifindex_table[ifp->if_index] == ifp);
MPASS(ifindex_table[ifp->if_index].ife_ifnet == ifp);
#ifdef VIMAGE
ifp->if_vnet = curvnet;
@ -4494,8 +4517,8 @@ if_show_ifnet(struct ifnet *ifp)
IF_DB_PRINTF("%d", if_dunit);
IF_DB_PRINTF("%s", if_description);
IF_DB_PRINTF("%u", if_index);
IF_DB_PRINTF("%d", if_idxgen);
IF_DB_PRINTF("%u", if_refcount);
IF_DB_PRINTF("%d", if_index_reserved);
IF_DB_PRINTF("%p", if_softc);
IF_DB_PRINTF("%p", if_l2com);
IF_DB_PRINTF("%p", if_llsoftc);
@ -4550,7 +4573,7 @@ DB_SHOW_ALL_COMMAND(ifnets, db_show_all_ifnets)
u_short idx;
for (idx = 1; idx <= if_index; idx++) {
ifp = ifindex_table[idx];
ifp = ifindex_table[idx].ife_ifnet;
if (ifp == NULL)
continue;
db_printf( "%20s ifp=%p\n", ifp->if_xname, ifp);

9
sys/net/if_var.h
View File

@ -334,7 +334,7 @@ struct ifnet {
const char *if_dname; /* driver name */
int if_dunit; /* unit or IF_DUNIT_NONE */
u_short if_index; /* numeric abbreviation for this if */
short if_index_reserved; /* spare space to grow if_index */
u_short if_idxgen; /* ... and its generation count */
char if_xname[IFNAMSIZ]; /* external name (name + unit) */
char *if_description; /* interface description */
@ -644,6 +644,13 @@ extern struct sx ifnet_sxlock;
struct ifnet *ifnet_byindex(u_int);
struct ifnet *ifnet_byindex_ref(u_int);
/*
* ifnet_byindexgen() looks up ifnet by index and generation count,
* attempting to restore a weak pointer that had been stored across
* the epoch.
*/
struct ifnet *ifnet_byindexgen(uint16_t idx, uint16_t gen);
VNET_DECLARE(struct ifnethead, ifnet);
VNET_DECLARE(struct ifgrouphead, ifg_head);
VNET_DECLARE(struct ifnet *, loif); /* first loopback interface */

6
sys/sys/mbuf.h
View File

@ -159,6 +159,10 @@ struct pkthdr {
union {
struct m_snd_tag *snd_tag; /* send tag, if any */
struct ifnet *rcvif; /* rcv interface */
struct {
uint16_t rcvidx; /* rcv interface index ... */
uint16_t rcvgen; /* ... and generation count */
};
};
SLIST_HEAD(packet_tags, m_tag) tags; /* list of packet tags */
int32_t len; /* total packet length */
@ -862,6 +866,8 @@ int m_snd_tag_alloc(struct ifnet *,
void m_snd_tag_init(struct m_snd_tag *, struct ifnet *,
const struct if_snd_tag_sw *);
void m_snd_tag_destroy(struct m_snd_tag *);
void m_rcvif_serialize(struct mbuf *);
struct ifnet *m_rcvif_restore(struct mbuf *);
static __inline int
m_gettype(int size)