Skip to content

usb-linux: Support larger usbmon ring buffer limit #1555

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

usb-linux: Support larger usbmon ring buffer limit #1555

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
73 changes: 50 additions & 23 deletions pcap-usb-linux.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -211,10 +211,15 @@ usb_findalldevs(pcap_if_list_t *devlistp, char *err_str)
}

/*
* Matches what's in mon_bin.c in the Linux kernel.
* Matches what's in mon_bin.c in older Linux kernels.
*/
#define MIN_RING_SIZE (8*1024)
#define MAX_RING_SIZE (1200*1024)
#define MIN_RING_SIZE (8*1024)
#define MAX_RING_SIZE_1200K (1200*1024)

/*
* The maximum ring size in newer kernels.
*/
#define MAX_RING_SIZE_64M (64*1024*1024)

static int
usb_set_ring_size(pcap_t* handle, int header_size)
Expand All @@ -226,10 +231,10 @@ usb_set_ring_size(pcap_t* handle, int header_size)
* 2) descriptors, for isochronous transfers;
* 3) the payload.
*
* The kernel buffer has a size, defaulting to 300KB, with a
* minimum of 8KB and a maximum of 1200KB. The size is set with
* the MON_IOCT_RING_SIZE ioctl; the size passed in is rounded up
* to a page size.
* The kernel buffer has a size, defaulting to 300 KiB, with a
* minimum of 8 KiB and a maximum of 64 MiB (1200 KiB on older
* kernels). The size is set with the MON_IOCT_RING_SIZE ioctl;
* the size passed in is rounded up to a page size.
*
* No more than {buffer size}/5 bytes worth of payload is saved.
* Therefore, if we subtract the fixed-length size from the
Expand All @@ -248,18 +253,19 @@ usb_set_ring_size(pcap_t* handle, int header_size)

/*
* Will this get an error?
* (There's no way to query the minimum or maximum, so we just
* copy the value from the kernel source. We don't round it
* up to a multiple of the page size.)
* (There's no way to query the minimum or maximum, so we start
* with the new maximum, and, if that fails with EINVAL, try
* the old maximum. We don't round it up to a multiple of the
* page size.)
*/
if (ring_size > MAX_RING_SIZE) {
if (ring_size > MAX_RING_SIZE_64M) {
/*
* Yes. Lower the ring size to the maximum, and set the
* snapshot length to the value that would give us a
* maximum-size ring.
*/
ring_size = MAX_RING_SIZE;
handle->snapshot = header_size + (MAX_RING_SIZE/5);
ring_size = MAX_RING_SIZE_64M;
handle->snapshot = header_size + (MAX_RING_SIZE_64M/5);
} else if (ring_size < MIN_RING_SIZE) {
/*
* Yes. Raise the ring size to the minimum, but leave
Expand All @@ -270,12 +276,36 @@ usb_set_ring_size(pcap_t* handle, int header_size)
ring_size = MIN_RING_SIZE;
}

if (ioctl(handle->fd, MON_IOCT_RING_SIZE, ring_size) == -1) {
pcapint_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
errno, "Can't set ring size from fd %d", handle->fd);
return -1;
if (ioctl(handle->fd, MON_IOCT_RING_SIZE, ring_size) == 0) {
/* It worked. */
return ring_size;
}

/*
* It failed. If the error was EINVAL, and the ring size
* was bigger than the old maximum, we may be on a kernel
* that doesn't support ring sizes that large.
*/
if (errno == EINVAL && ring_size > MAX_RING_SIZE_1200K) {
/*
* Try again with the old maximum.
*/
ring_size = MAX_RING_SIZE_1200K;
handle->snapshot = header_size + (MAX_RING_SIZE_1200K/5);
if (ioctl(handle->fd, MON_IOCT_RING_SIZE, ring_size) == 0) {
/* That worked. */
return ring_size;
}
}
return ring_size;

/*
* Either the first ioctl failed for some reason other than
* EINVAL with a ring size bigger than the old maximum, or
* the second one failed. Report the error.
*/
pcapint_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
errno, "Can't set ring size from fd %d", handle->fd);
return -1;
}

static
Expand Down Expand Up @@ -461,12 +491,9 @@ usb_activate(pcap_t* handle)
* Turn a negative snapshot value (invalid), a snapshot value of
* 0 (unspecified), or a value bigger than the normal maximum
* value, into the maximum allowed value.
*
* If some application really *needs* a bigger snapshot
* length, we should just increase MAXIMUM_SNAPLEN.
*/
if (handle->snapshot <= 0 || handle->snapshot > MAXIMUM_SNAPLEN)
handle->snapshot = MAXIMUM_SNAPLEN;
if (handle->snapshot <= 0 || handle->snapshot > MAX_RING_SIZE_64M/5)
handle->snapshot = MAX_RING_SIZE_64M/5;

/* Initialize some components of the pcap structure. */
handle->bufsize = handle->snapshot;
Expand Down