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|
/*
* Attempt to set up memory-mapped access.
*
* On success, returns 1, and sets *status to 0 if there are no warnings
* or to a PCAP_WARNING_ code if there is a warning.
*
* On failure due to lack of support for memory-mapped capture, returns
* 0.
*
* On error, returns -1, and sets *status to the appropriate error code;
* if that is PCAP_ERROR, sets handle->errbuf to the appropriate message.
*/
static int
create_ring(pcap_t *handle, int *status)
{
unsigned i, j, frames_per_block;
struct tpacket_req req;
socklen_t len;
unsigned int sk_type, tp_reserve, maclen, tp_hdrlen, netoff, macoff;
unsigned int frame_size;
/*
* Start out assuming no warnings or errors.
*/
*status = 0;
/* Note that with large snapshot length (say 64K, which is the default
* for recent versions of tcpdump, the value that "-s 0" has given
* for a long time with tcpdump, and the default in Wireshark/TShark),
* if we use the snapshot length to calculate the frame length,
* only a few frames will be available in the ring even with pretty
* large ring size (and a lot of memory will be unused).
*
* Ideally, we should choose a frame length based on the
* minimum of the specified snapshot length and the maximum
* packet size. That's not as easy as it sounds; consider, for
* example, an 802.11 interface in monitor mode, where the
* frame would include a radiotap header, where the maximum
* radiotap header length is device-dependent.
*
* So, for now, we just do this for Ethernet devices, where
* there's no metadata header, and the link-layer header is
* fixed length. We can get the maximum packet size by
* adding 18, the Ethernet header length plus the CRC length
* (just in case we happen to get the CRC in the packet), to
* the MTU of the interface; we fetch the MTU in the hopes
* that it reflects support for jumbo frames. (Even if the
* interface is just being used for passive snooping, the driver
* might set the size of buffers in the receive ring based on
* the MTU, so that the MTU limits the maximum size of packets
* that we can receive.)
*
* We don't do that if segmentation/fragmentation or receive
* offload are enabled, so we don't get rudely surprised by
* "packets" bigger than the MTU. */
frame_size = handle->snapshot;
if (handle->linktype == DLT_EN10MB) {
int mtu;
int offload;
offload = iface_get_offload(handle);
if (offload == -1) {
*status = PCAP_ERROR;
return -1;
}
if (!offload) {
mtu = iface_get_mtu(handle->fd, handle->opt.source,
handle->errbuf);
if (mtu == -1) {
*status = PCAP_ERROR;
return -1;
}
if (frame_size > mtu + 18)
frame_size = mtu + 18;
}
}
/* NOTE: calculus matching those in tpacket_rcv()
* in linux-2.6/net/packet/af_packet.c
*/
len = sizeof(sk_type);
if (getsockopt(handle->fd, SOL_SOCKET, SO_TYPE, &sk_type, &len) < 0) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "getsockopt: %s", pcap_strerror(errno));
*status = PCAP_ERROR;
return -1;
}
#ifdef PACKET_RESERVE
len = sizeof(tp_reserve);
if (getsockopt(handle->fd, SOL_PACKET, PACKET_RESERVE, &tp_reserve, &len) < 0) {
if (errno != ENOPROTOOPT) {
/*
* ENOPROTOOPT means "kernel doesn't support
* PACKET_RESERVE", in which case we fall back
* as best we can.
*/
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "getsockopt: %s", pcap_strerror(errno));
*status = PCAP_ERROR;
return -1;
}
tp_reserve = 0; /* older kernel, reserve not supported */
}
#else
tp_reserve = 0; /* older kernel, reserve not supported */
#endif
maclen = (sk_type == SOCK_DGRAM) ? 0 : MAX_LINKHEADER_SIZE;
/* XXX: in the kernel maclen is calculated from
* LL_ALLOCATED_SPACE(dev) and vnet_hdr.hdr_len
* in: packet_snd() in linux-2.6/net/packet/af_packet.c
* then packet_alloc_skb() in linux-2.6/net/packet/af_packet.c
* then sock_alloc_send_pskb() in linux-2.6/net/core/sock.c
* but I see no way to get those sizes in userspace,
* like for instance with an ifreq ioctl();
* the best thing I've found so far is MAX_HEADER in the kernel
* part of linux-2.6/include/linux/netdevice.h
* which goes up to 128+48=176; since pcap-linux.c defines
* a MAX_LINKHEADER_SIZE of 256 which is greater than that,
* let's use it.. maybe is it even large enough to directly
* replace macoff..
*/
tp_hdrlen = TPACKET_ALIGN(handle->md.tp_hdrlen) + sizeof(struct sockaddr_ll) ;
netoff = TPACKET_ALIGN(tp_hdrlen + (maclen < 16 ? 16 : maclen)) + tp_reserve;
/* NOTE: AFAICS tp_reserve may break the TPACKET_ALIGN of
* netoff, which contradicts
* linux-2.6/Documentation/networking/packet_mmap.txt
* documenting that:
* "- Gap, chosen so that packet data (Start+tp_net)
* aligns to TPACKET_ALIGNMENT=16"
*/
/* NOTE: in linux-2.6/include/linux/skbuff.h:
* "CPUs often take a performance hit
* when accessing unaligned memory locations"
*/
macoff = netoff - maclen;
req.tp_frame_size = TPACKET_ALIGN(macoff + frame_size);
req.tp_frame_nr = handle->opt.buffer_size/req.tp_frame_size;
/* compute the minumum block size that will handle this frame.
* The block has to be page size aligned.
* The max block size allowed by the kernel is arch-dependent and
* it's not explicitly checked here. */
req.tp_block_size = getpagesize();
while (req.tp_block_size < req.tp_frame_size)
req.tp_block_size <<= 1;
frames_per_block = req.tp_block_size/req.tp_frame_size;
/*
* PACKET_TIMESTAMP was added after linux/net_tstamp.h was,
* so we check for PACKET_TIMESTAMP. We check for
* linux/net_tstamp.h just in case a system somehow has
* PACKET_TIMESTAMP but not linux/net_tstamp.h; that might
* be unnecessary.
*
* SIOCSHWTSTAMP was introduced in the patch that introduced
* linux/net_tstamp.h, so we don't bother checking whether
* SIOCSHWTSTAMP is defined (if your Linux system has
* linux/net_tstamp.h but doesn't define SIOCSHWTSTAMP, your
* Linux system is badly broken).
*/
#if defined(HAVE_LINUX_NET_TSTAMP_H) && defined(PACKET_TIMESTAMP)
/*
* If we were told to do so, ask the kernel and the driver
* to use hardware timestamps.
*
* Hardware timestamps are only supported with mmapped
* captures.
*/
if (handle->opt.tstamp_type == PCAP_TSTAMP_ADAPTER ||
handle->opt.tstamp_type == PCAP_TSTAMP_ADAPTER_UNSYNCED) {
struct hwtstamp_config hwconfig;
struct ifreq ifr;
int timesource;
/*
* Ask for hardware time stamps on all packets,
* including transmitted packets.
*/
memset(&hwconfig, 0, sizeof(hwconfig));
hwconfig.tx_type = HWTSTAMP_TX_ON;
hwconfig.rx_filter = HWTSTAMP_FILTER_ALL;
memset(&ifr, 0, sizeof(ifr));
strcpy(ifr.ifr_name, handle->opt.source);
ifr.ifr_data = (void *)&hwconfig;
if (ioctl(handle->fd, SIOCSHWTSTAMP, &ifr) < 0) {
switch (errno) {
case EPERM:
/*
* Treat this as an error, as the
* user should try to run this
* with the appropriate privileges -
* and, if they can't, shouldn't
* try requesting hardware time stamps.
*/
*status = PCAP_ERROR_PERM_DENIED;
return -1;
case EOPNOTSUPP:
/*
* Treat this as a warning, as the
* only way to fix the warning is to
* get an adapter that supports hardware
* time stamps. We'll just fall back
* on the standard host time stamps.
*/
*status = PCAP_WARNING_TSTAMP_TYPE_NOTSUP;
break;
default:
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"SIOCSHWTSTAMP failed: %s",
pcap_strerror(errno));
*status = PCAP_ERROR;
return -1;
}
} else {
/*
* Well, that worked. Now specify the type of
* hardware time stamp we want for this
* socket.
*/
if (handle->opt.tstamp_type == PCAP_TSTAMP_ADAPTER) {
/*
* Hardware timestamp, synchronized
* with the system clock.
*/
timesource = SOF_TIMESTAMPING_SYS_HARDWARE;
} else {
/*
* PCAP_TSTAMP_ADAPTER_UNSYNCED - hardware
* timestamp, not synchronized with the
* system clock.
*/
timesource = SOF_TIMESTAMPING_RAW_HARDWARE;
}
if (setsockopt(handle->fd, SOL_PACKET, PACKET_TIMESTAMP,
(void *)×ource, sizeof(timesource))) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"can't set PACKET_TIMESTAMP: %s",
pcap_strerror(errno));
*status = PCAP_ERROR;
return -1;
}
}
}
#endif /* HAVE_LINUX_NET_TSTAMP_H && PACKET_TIMESTAMP */
/* ask the kernel to create the ring */
retry:
req.tp_block_nr = req.tp_frame_nr / frames_per_block;
/* req.tp_frame_nr is requested to match frames_per_block*req.tp_block_nr */
req.tp_frame_nr = req.tp_block_nr * frames_per_block;
if (setsockopt(handle->fd, SOL_PACKET, PACKET_RX_RING,
(void *) &req, sizeof(req))) {
if ((errno == ENOMEM) && (req.tp_block_nr > 1)) {
/*
* Memory failure; try to reduce the requested ring
* size.
*
* We used to reduce this by half -- do 5% instead.
* That may result in more iterations and a longer
* startup, but the user will be much happier with
* the resulting buffer size.
*/
if (req.tp_frame_nr < 20)
req.tp_frame_nr -= 1;
else
req.tp_frame_nr -= req.tp_frame_nr/20;
goto retry;
}
if (errno == ENOPROTOOPT) {
/*
* We don't have ring buffer support in this kernel.
*/
return 0;
}
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"can't create rx ring on packet socket: %s",
pcap_strerror(errno));
*status = PCAP_ERROR;
return -1;
}
/* memory map the rx ring */
handle->md.mmapbuflen = req.tp_block_nr * req.tp_block_size;
handle->md.mmapbuf = mmap(0, handle->md.mmapbuflen,
PROT_READ|PROT_WRITE, MAP_SHARED, handle->fd, 0);
if (handle->md.mmapbuf == MAP_FAILED) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"can't mmap rx ring: %s", pcap_strerror(errno));
/* clear the allocated ring on error*/
destroy_ring(handle);
*status = PCAP_ERROR;
return -1;
}
/* allocate a ring for each frame header pointer*/
handle->cc = req.tp_frame_nr;
handle->buffer = malloc(handle->cc * sizeof(union thdr *));
if (!handle->buffer) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"can't allocate ring of frame headers: %s",
pcap_strerror(errno));
destroy_ring(handle);
*status = PCAP_ERROR;
return -1;
}
/* fill the header ring with proper frame ptr*/
handle->offset = 0;
for (i=0; i<req.tp_block_nr; ++i) {
void *base = &handle->md.mmapbuf[i*req.tp_block_size];
for (j=0; j<frames_per_block; ++j, ++handle->offset) {
RING_GET_FRAME(handle) = base;
base += req.tp_frame_size;
}
}
handle->bufsize = req.tp_frame_size;
handle->offset = 0;
return 1;
} |
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