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pf: Count holes rather than fragments for reassembly

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Avoid traversing the list of fragment entris to check whether the
pf(4) reassembly is complete.  Instead count the holes that are
created when inserting a fragment.  If there are no holes left, the
fragments are continuous.

Obtained from:	OpenBSD
Differential Revision:	https://reviews.freebsd.org/D17732
This commit is contained in:
Kristof Provost 2018-11-02 15:23:57 +00:00
parent 46b05e1923
commit 2b1c354ee6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=340060
1 changed files with 45 additions and 38 deletions
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83
sys/netpfil/pf/pf_norm.c
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@ -2,7 +2,7 @@
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright 2001 Niels Provos <provos@citi.umich.edu>
* Copyright 2011 Alexander Bluhm <bluhm@openbsd.org>
* Copyright 2011-2018 Alexander Bluhm <bluhm@openbsd.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -91,6 +91,7 @@ struct pf_fragment {
TAILQ_ENTRY(pf_fragment) frag_next;
uint32_t fr_timeout;
uint16_t fr_maxlen; /* maximum length of single fragment */
u_int16_t fr_holes; /* number of holes in the queue */
TAILQ_HEAD(pf_fragq, pf_frent) fr_queue;
};
@ -132,11 +133,11 @@ static void pf_remove_fragment(struct pf_fragment *);
static int pf_normalize_tcpopt(struct pf_rule *, struct mbuf *,
struct tcphdr *, int, sa_family_t);
static struct pf_frent *pf_create_fragment(u_short *);
static int pf_frent_holes(struct pf_frent *frent);
static struct pf_fragment *pf_find_fragment(struct pf_fragment_cmp *key,
struct pf_frag_tree *tree);
static struct pf_fragment *pf_fillup_fragment(struct pf_fragment_cmp *,
struct pf_frent *, u_short *);
static int pf_isfull_fragment(struct pf_fragment *);
static struct mbuf *pf_join_fragment(struct pf_fragment *);
#ifdef INET
static void pf_scrub_ip(struct mbuf **, uint32_t, uint8_t, uint8_t);
@ -333,6 +334,39 @@ pf_create_fragment(u_short *reason)
return (frent);
}
/*
* Calculate the additional holes that were created in the fragment
* queue by inserting this fragment. A fragment in the middle
* creates one more hole by splitting. For each connected side,
* it loses one hole.
* Fragment entry must be in the queue when calling this function.
*/
static int
pf_frent_holes(struct pf_frent *frent)
{
struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next);
struct pf_frent *next = TAILQ_NEXT(frent, fr_next);
int holes = 1;
if (prev == NULL) {
if (frent->fe_off == 0)
holes--;
} else {
KASSERT(frent->fe_off != 0, ("frent->fe_off != 0"));
if (frent->fe_off == prev->fe_off + prev->fe_len)
holes--;
}
if (next == NULL) {
if (!frent->fe_mff)
holes--;
} else {
KASSERT(frent->fe_mff, ("frent->fe_mff"));
if (next->fe_off == frent->fe_off + frent->fe_len)
holes--;
}
return holes;
}
static struct pf_fragment *
pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent,
u_short *reason)
@ -384,6 +418,7 @@ pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent,
*(struct pf_fragment_cmp *)frag = *key;
frag->fr_timeout = time_uptime;
frag->fr_maxlen = frent->fe_len;
frag->fr_holes = 1;
TAILQ_INIT(&frag->fr_queue);
RB_INSERT(pf_frag_tree, &V_pf_frag_tree, frag);
@ -391,6 +426,7 @@ pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent,
/* We do not have a previous fragment. */
TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next);
frag->fr_holes += pf_frent_holes(frent);
return (frag);
}
@ -457,6 +493,7 @@ pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent,
/* This fragment is completely overlapped, lose it. */
next = TAILQ_NEXT(after, fr_next);
frag->fr_holes -= pf_frent_holes(after);
m_freem(after->fe_m);
TAILQ_REMOVE(&frag->fr_queue, after, fr_next);
uma_zfree(V_pf_frent_z, after);
@ -466,6 +503,7 @@ pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent,
TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next);
else
TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next);
frag->fr_holes += pf_frent_holes(frent);
return (frag);
@ -476,40 +514,6 @@ pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent,
return (NULL);
}
static int
pf_isfull_fragment(struct pf_fragment *frag)
{
struct pf_frent *frent, *next;
uint16_t off, total;
/* Check if we are completely reassembled */
if (TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff)
return (0);
/* Maximum data we have seen already */
total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
/* Check if we have all the data */
off = 0;
for (frent = TAILQ_FIRST(&frag->fr_queue); frent; frent = next) {
next = TAILQ_NEXT(frent, fr_next);
off += frent->fe_len;
if (off < total && (next == NULL || next->fe_off != off)) {
DPFPRINTF(("missing fragment at %d, next %d, total %d",
off, next == NULL ? -1 : next->fe_off, total));
return (0);
}
}
DPFPRINTF(("%d < %d?", off, total));
if (off < total)
return (0);
KASSERT(off == total, ("off == total"));
return (1);
}
static struct mbuf *
pf_join_fragment(struct pf_fragment *frag)
{
@ -570,8 +574,10 @@ pf_reassemble(struct mbuf **m0, struct ip *ip, int dir, u_short *reason)
/* The mbuf is part of the fragment entry, no direct free or access */
m = *m0 = NULL;
if (!pf_isfull_fragment(frag))
if (frag->fr_holes) {
DPFPRINTF(("frag %d, holes %d", frag->fr_id, frag->fr_holes));
return (PF_PASS); /* drop because *m0 is NULL, no error */
}
/* We have all the data */
frent = TAILQ_FIRST(&frag->fr_queue);
@ -654,7 +660,8 @@ pf_reassemble6(struct mbuf **m0, struct ip6_hdr *ip6, struct ip6_frag *fraghdr,
/* The mbuf is part of the fragment entry, no direct free or access. */
m = *m0 = NULL;
if (!pf_isfull_fragment(frag)) {
if (frag->fr_holes) {
DPFPRINTF(("frag %d, holes %d", frag->fr_id, frag->fr_holes));
PF_FRAG_UNLOCK();
return (PF_PASS); /* Drop because *m0 is NULL, no error. */
}