Author: glebius
Date: Sun Mar 10 17:20:09 2019
New Revision: 344980
URL: https://svnweb.freebsd.org/changeset/base/344980
Log:
Most Ethernet drivers that potentially can run a pfil(9) hook with
PFIL_MEMPTR flag are intentionally providing a memory address that
isn't aligned to pointer alignment. This is done to align an IPv4
or IPv6 header that is expected to follow Ethernet header.
When we return PFIL_REALLOCED we store a pointer to allocated mbuf
at this address. With this change the KPI changes to store the pointer
at aligned address, which usually yields in +2 bytes.
Provide two inlines:
pfil_packet_align() to get aligned pfil_packet_t for a misaligned one
pfil_mem2mbuf() to read out mbuf pointer from misaligned pfil_packet_t
Provide function pfil_realloc(), not used yet, that would convert a
memory pfil_packet_t to an mbuf one.
Reported by: hps
Reviewed by: hps, gallatin
Modified:
head/sys/net/pfil.c
head/sys/net/pfil.h
Modified: head/sys/net/pfil.c
==============================================================================
--- head/sys/net/pfil.c Sun Mar 10 17:08:05 2019 (r344979)
+++ head/sys/net/pfil.c Sun Mar 10 17:20:09 2019 (r344980)
@@ -118,15 +118,31 @@ VNET_DEFINE_STATIC(struct pfilhookhead, pfil_hook_list
static struct pfil_link *pfil_link_remove(pfil_chain_t *, pfil_hook_t );
static void pfil_link_free(epoch_context_t);
+int
+pfil_realloc(pfil_packet_t *p, int flags, struct ifnet *ifp)
+{
+ struct mbuf *m;
+
+ MPASS(flags & PFIL_MEMPTR);
+
+ if ((m = m_devget(p->mem, PFIL_LENGTH(flags), 0, ifp, NULL)) == NULL)
+ return (ENOMEM);
+ *p = pfil_packet_align(*p);
+ *p->m = m;
+
+ return (0);
+}
+
static __noinline int
-pfil_fake_mbuf(pfil_func_t func, void *mem, struct ifnet *ifp, int flags,
+pfil_fake_mbuf(pfil_func_t func, pfil_packet_t *p, struct ifnet *ifp, int
flags,
void *ruleset, struct inpcb *inp)
{
struct mbuf m, *mp;
pfil_return_t rv;
(void)m_init(&m, M_NOWAIT, MT_DATA, M_NOFREE | M_PKTHDR);
- m_extadd(&m, mem, PFIL_LENGTH(flags), NULL, NULL, NULL, 0, EXT_RXRING);
+ m_extadd(&m, p->mem, PFIL_LENGTH(flags), NULL, NULL, NULL, 0,
+ EXT_RXRING);
m.m_len = m.m_pkthdr.len = PFIL_LENGTH(flags);
mp = &m;
flags &= ~(PFIL_MEMPTR | PFIL_LENMASK);
@@ -135,10 +151,11 @@ pfil_fake_mbuf(pfil_func_t func, void *mem, struct ifn
if (rv == PFIL_PASS && mp != &m) {
/*
* Firewalls that need pfil_fake_mbuf() most likely don't
- * know to return PFIL_REALLOCED.
+ * know they need return PFIL_REALLOCED.
*/
rv = PFIL_REALLOCED;
- *(struct mbuf **)mem = mp;
+ *p = pfil_packet_align(*p);
+ *p->m = mp;
}
return (rv);
@@ -168,8 +185,8 @@ pfil_run_hooks(struct pfil_head *head, pfil_packet_t p
PFIL_EPOCH_ENTER(et);
CK_STAILQ_FOREACH(link, pch, link_chain) {
if ((flags & PFIL_MEMPTR) && !(link->link_flags & PFIL_MEMPTR))
- rv = pfil_fake_mbuf(link->link_func, p.mem, ifp,
- flags, link->link_ruleset, inp);
+ rv = pfil_fake_mbuf(link->link_func, &p, ifp, flags,
+ link->link_ruleset, inp);
else
rv = (*link->link_func)(p, ifp, flags,
link->link_ruleset, inp);
Modified: head/sys/net/pfil.h
==============================================================================
--- head/sys/net/pfil.h Sun Mar 10 17:08:05 2019 (r344979)
+++ head/sys/net/pfil.h Sun Mar 10 17:20:09 2019 (r344980)
@@ -98,8 +98,25 @@ struct inpcb;
typedef union {
struct mbuf **m;
void *mem;
+ uintptr_t __ui;
} pfil_packet_t __attribute__((__transparent_union__));
+static inline pfil_packet_t
+pfil_packet_align(pfil_packet_t p)
+{
+
+ return ((pfil_packet_t ) (((uintptr_t)(p).mem +
+ (_Alignof(void *) - 1)) & - _Alignof(void *)));
+}
+
+static inline struct mbuf *
+pfil_mem2mbuf(void *v)
+{
+
+ return (*(struct mbuf **) (((uintptr_t)(v) +
+ (_Alignof(void *) - 1)) & - _Alignof(void *)));
+}
+
typedef enum {
PFIL_PASS = 0,
PFIL_DROPPED,
@@ -187,6 +204,11 @@ struct _pfil_head {
};
#define PFIL_HOOKED_IN(p) (((struct _pfil_head *)(p))->head_nhooksin >
0)
#define PFIL_HOOKED_OUT(p) (((struct _pfil_head *)(p))->head_nhooksout
> 0)
+
+/*
+ * Alloc mbuf to be used instead of memory pointer.
+ */
+int pfil_realloc(pfil_packet_t *, int, struct ifnet *);
#endif /* _KERNEL */
#endif /* _NET_PFIL_H_ */
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