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Unmapped mbufs allow sendfile to carry multiple pages of data in a single mbuf, without mapping those pages. It is a requirement for Netflix's in-kernel TLS, and provides a 5-10% CPU savings on heavy web serving workloads when used by sendfile, due to effectively compressing socket buffers by an order of magnitude, and hence reducing cache misses. For this new external mbuf buffer type (EXT_PGS), the ext_buf pointer now points to a struct mbuf_ext_pgs structure instead of a data buffer. This structure contains an array of physical addresses (this reduces cache misses compared to an earlier version that stored an array of vm_page_t pointers). It also stores additional fields needed for in-kernel TLS such as the TLS header and trailer data that are currently unused. To more easily detect these mbufs, the M_NOMAP flag is set in m_flags in addition to M_EXT. Various functions like m_copydata() have been updated to safely access packet contents (using uiomove_fromphys()), to make things like BPF safe. NIC drivers advertise support for unmapped mbufs on transmit via a new IFCAP_NOMAP capability. This capability can be toggled via the new 'nomap' and '-nomap' ifconfig(8) commands. For NIC drivers that only transmit packet contents via DMA and use bus_dma, adding the capability to if_capabilities and if_capenable should be all that is required. If a NIC does not support unmapped mbufs, they are converted to a chain of mapped mbufs (using sf_bufs to provide the mapping) in ip_output or ip6_output. If an unmapped mbuf requires software checksums, it is also converted to a chain of mapped mbufs before computing the checksum. Submitted by: gallatin (earlier version) Reviewed by: gallatin, hselasky, rrs Discussed with: ae, kp (firewalls) Relnotes: yes Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D20616
215 lines
6.4 KiB
C
215 lines
6.4 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 2007 Seccuris Inc.
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* All rights reserved.
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*
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* This software was developed by Robert N. M. Watson under contract to
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* Seccuris Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* Copyright (c) 1990, 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from the Stanford/CMU enet packet filter,
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* (net/enet.c) distributed as part of 4.3BSD, and code contributed
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* to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
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* Berkeley Laboratory.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)bpf.c 8.4 (Berkeley) 1/9/95
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_bpf.h"
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#include <sys/param.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mbuf.h>
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#include <sys/mutex.h>
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#include <sys/socket.h>
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#include <sys/uio.h>
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#include <sys/kernel.h>
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#include <sys/sysctl.h>
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#include <net/if.h>
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#include <net/bpf.h>
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#include <net/bpf_buffer.h>
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#include <net/bpfdesc.h>
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/*
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* Implement historical kernel memory buffering model for BPF: two malloc(9)
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* kernel buffers are hung off of the descriptor. The size is fixed prior to
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* attaching to an ifnet, ad cannot be changed after that. read(2) simply
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* copies the data to user space using uiomove(9).
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*/
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static int bpf_bufsize = 4096;
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SYSCTL_INT(_net_bpf, OID_AUTO, bufsize, CTLFLAG_RW,
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&bpf_bufsize, 0, "Default capture buffer size in bytes");
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static int bpf_maxbufsize = BPF_MAXBUFSIZE;
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SYSCTL_INT(_net_bpf, OID_AUTO, maxbufsize, CTLFLAG_RW,
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&bpf_maxbufsize, 0, "Maximum capture buffer in bytes");
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/*
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* Simple data copy to the current kernel buffer.
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*/
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void
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bpf_buffer_append_bytes(struct bpf_d *d, caddr_t buf, u_int offset,
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void *src, u_int len)
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{
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u_char *src_bytes;
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src_bytes = (u_char *)src;
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bcopy(src_bytes, buf + offset, len);
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}
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/*
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* Scatter-gather data copy from an mbuf chain to the current kernel buffer.
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*/
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void
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bpf_buffer_append_mbuf(struct bpf_d *d, caddr_t buf, u_int offset, void *src,
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u_int len)
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{
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const struct mbuf *m;
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u_char *dst;
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m = (struct mbuf *)src;
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dst = (u_char *)buf + offset;
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m_copydata(m, 0, len, dst);
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}
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/*
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* Free BPF kernel buffers on device close.
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*/
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void
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bpf_buffer_free(struct bpf_d *d)
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{
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if (d->bd_sbuf != NULL)
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free(d->bd_sbuf, M_BPF);
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if (d->bd_hbuf != NULL)
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free(d->bd_hbuf, M_BPF);
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if (d->bd_fbuf != NULL)
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free(d->bd_fbuf, M_BPF);
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#ifdef INVARIANTS
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d->bd_sbuf = d->bd_hbuf = d->bd_fbuf = (caddr_t)~0;
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#endif
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}
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/*
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* This is a historical initialization that occurs when the BPF descriptor is
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* first opened. It does not imply selection of a buffer mode, so we don't
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* allocate buffers here.
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*/
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void
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bpf_buffer_init(struct bpf_d *d)
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{
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d->bd_bufsize = bpf_bufsize;
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}
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/*
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* Allocate or resize buffers.
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*/
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int
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bpf_buffer_ioctl_sblen(struct bpf_d *d, u_int *i)
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{
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u_int size;
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caddr_t fbuf, sbuf;
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size = *i;
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if (size > bpf_maxbufsize)
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*i = size = bpf_maxbufsize;
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else if (size < BPF_MINBUFSIZE)
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*i = size = BPF_MINBUFSIZE;
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/* Allocate buffers immediately */
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fbuf = (caddr_t)malloc(size, M_BPF, M_WAITOK);
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sbuf = (caddr_t)malloc(size, M_BPF, M_WAITOK);
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BPFD_LOCK(d);
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if (d->bd_bif != NULL) {
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/* Interface already attached, unable to change buffers */
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BPFD_UNLOCK(d);
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free(fbuf, M_BPF);
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free(sbuf, M_BPF);
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return (EINVAL);
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}
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/* Free old buffers if set */
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if (d->bd_fbuf != NULL)
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free(d->bd_fbuf, M_BPF);
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if (d->bd_sbuf != NULL)
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free(d->bd_sbuf, M_BPF);
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/* Fill in new data */
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d->bd_bufsize = size;
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d->bd_fbuf = fbuf;
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d->bd_sbuf = sbuf;
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d->bd_hbuf = NULL;
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d->bd_slen = 0;
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d->bd_hlen = 0;
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BPFD_UNLOCK(d);
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return (0);
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}
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/*
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* Copy buffer storage to user space in read().
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*/
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int
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bpf_buffer_uiomove(struct bpf_d *d, caddr_t buf, u_int len, struct uio *uio)
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{
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return (uiomove(buf, len, uio));
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}
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