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domain: make it safer to add domains post-domainfinalize

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I can see two concerns for adding domains after domainfinalize:

1.) The slow/fast callouts have already been setup.
2.) Userland could create a socket while we're in the middle of
  initialization.

We can address #1 fairly easily by tracking whether the domain's been
initialized for at least the default vnet. There are still some concerns
about the callbacks being invoked while a vnet is in the process of
being created/destroyed, but this is a pre-existing issue that the
callbacks must coordinate anyways.

We should also address #2, but technically this has been an issue
anyways because we don't assert on post-domainfinalize additions; we
don't seem to hit it in practice.

Future work can fix that up to make sure we don't find partially
constructed domains, but care must be taken to make sure that at least,
e.g., the usages of pffindproto in ip_input.c can still find them.

Differential Revision:	https://reviews.freebsd.org/D25459
This commit is contained in:
Kyle Evans 2020-06-25 21:38:27 -05:00
parent 625932c9aa
commit 29e400e994
2 changed files with 17 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
sys/kern/uipc_domain.c
View File

@ -47,6 +47,8 @@ __FBSDID("$FreeBSD$");
#include <sys/socketvar.h>
#include <sys/systm.h>
#include <machine/atomic.h>
#include <net/vnet.h>
/*
@ -177,6 +179,8 @@ domain_init(void *arg)
flags = atomic_load_acq_int(&dp->dom_flags);
if ((flags & DOMF_SUPPORTED) == 0)
return;
KASSERT((flags & DOMF_INITED) == 0 || !IS_DEFAULT_VNET(curvnet),
("Premature initialization of domain in non-default vnet"));
if (dp->dom_init)
(*dp->dom_init)();
for (pr = dp->dom_protosw; pr < dp->dom_protoswNPROTOSW; pr++)
@ -188,6 +192,8 @@ domain_init(void *arg)
max_datalen = MHLEN - max_hdr;
if (max_datalen < 1)
panic("%s: max_datalen < 1", __func__);
if (IS_DEFAULT_VNET(curvnet))
atomic_set_rel_int(&dp->dom_flags, DOMF_INITED);
}
#ifdef VIMAGE
@ -236,15 +242,6 @@ domain_add(void *data)
if (domain_init_status < 1)
printf("WARNING: attempt to domain_add(%s) before "
"domaininit()\n", dp->dom_name);
#endif
#ifdef notyet
KASSERT(domain_init_status < 2,
("attempt to domain_add(%s) after domainfinalize()",
dp->dom_name));
#else
if (domain_init_status >= 2)
printf("WARNING: attempt to domain_add(%s) after "
"domainfinalize()\n", dp->dom_name);
#endif
mtx_unlock(&dom_mtx);
}
@ -491,10 +488,14 @@ pfslowtimo(void *arg)
struct protosw *pr;
NET_EPOCH_ENTER(et);
for (dp = domains; dp; dp = dp->dom_next)
for (dp = domains; dp; dp = dp->dom_next) {
if ((atomic_load_int(&dp->dom_flags) & DOMF_INITED) == 0)
continue;
atomic_thread_fence_acq();
for (pr = dp->dom_protosw; pr < dp->dom_protoswNPROTOSW; pr++)
if (pr->pr_slowtimo)
(*pr->pr_slowtimo)();
}
NET_EPOCH_EXIT(et);
callout_reset(&pfslow_callout, hz/2, pfslowtimo, NULL);
}
@ -507,10 +508,14 @@ pffasttimo(void *arg)
struct protosw *pr;
NET_EPOCH_ENTER(et);
for (dp = domains; dp; dp = dp->dom_next)
for (dp = domains; dp; dp = dp->dom_next) {
if ((atomic_load_int(&dp->dom_flags) & DOMF_INITED) == 0)
continue;
atomic_thread_fence_acq();
for (pr = dp->dom_protosw; pr < dp->dom_protoswNPROTOSW; pr++)
if (pr->pr_fasttimo)
(*pr->pr_fasttimo)();
}
NET_EPOCH_EXIT(et);
callout_reset(&pffast_callout, hz/5, pffasttimo, NULL);
}

1
sys/sys/domain.h
View File

@ -74,6 +74,7 @@ struct domain {
/* dom_flags */
#define DOMF_SUPPORTED 0x0001 /* System supports this domain. */
#define DOMF_INITED 0x0002 /* Initialized in the default vnet. */
#ifdef _KERNEL
extern int domain_init_status;