[SLOF] [PATCH v2 06/11] libnet: Add functions for downloading and parsing pxelinux.cfg files
Alexey Kardashevskiy
aik at ozlabs.ru
Thu May 24 19:02:03 AEST 2018
On 19/5/18 1:45 am, Thomas Huth wrote:
> Booting a kernel via pxelinux.cfg files is common on x86 and also with
> ppc64 bootloaders like petitboot, so it would be nice to support this
> in SLOF, too. This patch adds functions for downloading and parsing
> such pxelinux.cfg files. See this URL for more details on pxelinux.cfg:
> https://www.syslinux.org/wiki/index.php?title=PXELINUX
>
> Signed-off-by: Thomas Huth <thuth at redhat.com>
> ---
> lib/libnet/Makefile | 2 +-
> lib/libnet/pxelinux.c | 209 ++++++++++++++++++++++++++++++++++++++++++++++++++
> lib/libnet/pxelinux.h | 33 ++++++++
> 3 files changed, 243 insertions(+), 1 deletion(-)
> create mode 100644 lib/libnet/pxelinux.c
> create mode 100644 lib/libnet/pxelinux.h
>
> diff --git a/lib/libnet/Makefile b/lib/libnet/Makefile
> index dfefea9..a2a6570 100644
> --- a/lib/libnet/Makefile
> +++ b/lib/libnet/Makefile
> @@ -19,7 +19,7 @@ include $(TOP)/make.rules
> CFLAGS += -I. -I.. -I../libc/include -I$(TOP)/include $(FLAG)
>
> SRCS = ethernet.c ipv4.c udp.c tcp.c dns.c bootp.c dhcp.c tftp.c \
> - ipv6.c dhcpv6.c icmpv6.c ndp.c netload.c ping.c args.c
> + ipv6.c dhcpv6.c icmpv6.c ndp.c netload.c ping.c args.c pxelinux.c
>
> OBJS = $(SRCS:%.c=%.o)
>
> diff --git a/lib/libnet/pxelinux.c b/lib/libnet/pxelinux.c
> new file mode 100644
> index 0000000..0c0b42e
> --- /dev/null
> +++ b/lib/libnet/pxelinux.c
> @@ -0,0 +1,209 @@
> +/*****************************************************************************
> + * pxelinux.cfg-style config file support.
> + *
> + * See https://www.syslinux.org/wiki/index.php?title=PXELINUX for information
> + * about the pxelinux config file layout.
> + *
> + * Copyright 2018 Red Hat, Inc.
> + *
> + * This program and the accompanying materials are made available under the
> + * terms of the BSD License which accompanies this distribution, and is
> + * available at http://www.opensource.org/licenses/bsd-license.php
> + *
> + * Contributors:
> + * Thomas Huth, Red Hat Inc. - initial implementation
> + *****************************************************************************/
> +
> +#include <stdio.h>
> +#include <string.h>
> +#include "tftp.h"
> +#include "pxelinux.h"
> +
> +/**
> + * Call tftp() and report errors (excet "file-not-found" errors)
> + */
> +static int pxelinux_tftp_load(filename_ip_t *fnip, void *buffer, int len)
> +{
> + tftp_err_t tftp_err;
> + int rc;
> +
> + rc = tftp(fnip, buffer, len, &tftp_err);
> +
> + if (rc > 0) {
> + printf("\r TFTP: Received %s (%d bytes)\n",
> + fnip->filename, rc);
> + } else if (rc == -3) {
> + /* Ignore file-not-found (since we are probing the files)
> + * and simply erase the "Receiving data: 0 KBytes" string */
> + printf("\r \r");
> + } else {
> + const char *errstr = NULL;
> + rc = tftp_get_error_info(fnip, &tftp_err, rc, &errstr, NULL);
> + if (errstr)
> + printf("\r TFTP error: %s\n", errstr);
> + }
> +
> + return rc;
> +}
> +
> +/**
> + * Try to load a pxelinux.cfg file by probing the possible file names.
> + */
> +static int pxelinux_load_cfg(filename_ip_t *fn_ip, uint8_t *mac, uint8_t *uuid,
> + char *cfgbuf, int cfgbufsize)
> +{
> + int rc, idx;
> + char basedir[sizeof(fn_ip->filename) - 40];
Why 40? +40 would make sense to accommodate UUID but -40 I do not understand.
> + char *slash;
> +
> + cfgbuf[cfgbufsize - 1] = 0; /* Make sure it is NUL-terminated */
This should go to pxelinux_load_parse_cfg().
> +
> + /* Did we get a usable base directory via DHCP? */
> + slash = strrchr(fn_ip->filename, '/');
> + if (slash && slash - fn_ip->filename < sizeof(basedir) - 1) {
> + slash[1] = 0;
> + strcpy(basedir, fn_ip->filename);
> + } else {
> + strcpy(basedir, "pxelinux.cfg/");
If a long directory name was returned via DHCP, you'll end up here silently
using 'pxelinux.cfg/'.
> + }
> +
> + printf("Trying pxelinux.cfg files...\n");
> +
> + /* Try to load config file with name based on the VM UUID */
> + if (uuid) {
> + sprintf(fn_ip->filename, "%s%02x%02x%02x%02x-%02x%02x-"
> + "%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x", basedir,
> + uuid[0], uuid[1], uuid[2], uuid[3], uuid[4], uuid[5],
> + uuid[6], uuid[7], uuid[8], uuid[9], uuid[10], uuid[11],
> + uuid[12], uuid[13], uuid[14], uuid[15]);
> + rc = pxelinux_tftp_load(fn_ip, cfgbuf, cfgbufsize - 1);
> + if (rc > 0) {
> + return rc;
> + }
> + }
> +
> + /* Look for config file with MAC address in its name */
> + sprintf(fn_ip->filename, "%s%02x-%02x-%02x-%02x-%02x-%02x", basedir,
> + mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
> + rc = pxelinux_tftp_load(fn_ip, cfgbuf, cfgbufsize - 1);
> + if (rc > 0) {
> + return rc;
> + }
> +
> + /* Look for config file with IP address in its name */
> + if (fn_ip->ip_version == 4) {
> + for (idx = 0; idx <= 7; idx++) {
> + sprintf(fn_ip->filename, "%s%02X%02X%02X%02X", basedir,
> + (fn_ip->own_ip >> 24) & 0xff,
> + (fn_ip->own_ip >> 16) & 0xff,
> + (fn_ip->own_ip >> 8) & 0xff,
> + fn_ip->own_ip & 0xff);
You do not need to sprintf every iteration, you can do it once before for()
and then cut bytes from the end in this loop. Or it may change somewhere in
lib/libnet/tftp.c? I could not spot where.
> + fn_ip->filename[strlen(fn_ip->filename) - idx] = 0;
> + rc = pxelinux_tftp_load(fn_ip, cfgbuf, cfgbufsize - 1);
> + if (rc > 0) {
> + return rc;
> + }
> + }
> + }
> +
> + /* Try "default" config file */
> + sprintf(fn_ip->filename, "%sdefault", basedir);
> + rc = pxelinux_tftp_load(fn_ip, cfgbuf, cfgbufsize - 1);
> +
> + return rc;
> +}
> +
> +/**
> + * Parse a pxelinux-style configuration file.
> + * @param cfg Pointer to the buffer with contents of the config file
> + * @param cfgsize Size of the cfg buffer
> + * @param entries Pointer to array where the results should be put into
> + * @param max_entries Number of available slots in the entries array
> + * @param def_ent Used to return the index of the default entry
> + * @return Number of valid entries
> + */
> +int pxelinux_parse_cfg(char *cfg, int cfgsize, struct lkia *entries,
Are you planning on returning errors from this? If not, make "num_entries"
unsigned and then you can drop " > 0" in "num_entries > 0" below.
> + int max_entries, int *def_ent)
> +{
> + int num_entries = 0;
> + char *ptr = cfg, *nextptr, *eol, *arg;
> + char *defaultlabel = NULL;
> +
> + *def_ent = 0;
> +
> + while (ptr < cfg + cfgsize && num_entries < max_entries) {
> + eol = strchr(ptr, '\n');
> + if (!eol) {
> + eol = cfg + cfgsize;
> + }
> + nextptr = eol + 1;
> + do {
> + *eol-- = '\0'; /* Remove spaces, tabs and returns */
> + } while (eol >= ptr &&
> + (*eol == '\r' || *eol == ' ' || *eol == '\t'));
> + while (*ptr == ' ' || *ptr == '\t') {
> + ptr++;
> + }
> + if (*ptr == 0 || *ptr == '#') {
> + goto nextline; /* Ignore comments and empty lines */
> + }
> + arg = strchr(ptr, ' '); /* Search space between cmnd and arg */
> + if (!arg) {
> + arg = strchr(ptr, '\t');
> + }
> + if (!arg) {
> + printf("Failed to parse this line:\n %s\n", ptr);
> + goto nextline;
> + }
> + *arg++ = 0;
> + while (*arg == ' ' || *arg == '\t') {
> + arg++;
> + }
> + if (!strcasecmp("default", ptr)) {
> + defaultlabel = arg;
> + } else if (!strcasecmp("label", ptr)) {
> + entries[num_entries].label = arg;
> + if (defaultlabel && !strcmp(arg, defaultlabel)) {
> + *def_ent = num_entries;
> + }
> + num_entries++;
> + } else if (!strcasecmp("kernel", ptr) && num_entries > 0) {
> + entries[num_entries - 1].kernel = arg;
> + } else if (!strcasecmp("initrd", ptr) && num_entries > 0) {
> + entries[num_entries - 1].initrd = arg;
> + } else if (!strcasecmp("append", ptr) && num_entries > 0) {
> + entries[num_entries - 1].append = arg;
> + } else {
> + printf("Command '%s' is not supported.\n", ptr);
> + }
> +nextline:
> + ptr = nextptr;
> + }
> +
> + return num_entries;
> +}
> +
> +/**
> + * Try to load and parse a pxelinux-style configuration file.
> + * @param fn_ip must contain server and client IP information
> + * @param mac MAC address which should be used for probing
> + * @param uuid UUID which should be used for probing (can be NULL)
> + * @param cfgbuf Pointer to the buffer where config file should be loaded
> + * @param cfgsize Size of the cfgbuf buffer
> + * @param entries Pointer to array where the results should be put into
> + * @param max_entries Number of available slots in the entries array
> + * @param def_ent Used to return the index of the default entry
> + * @return Number of valid entries
> + */
> +int pxelinux_load_parse_cfg(filename_ip_t *fn_ip, uint8_t *mac, uint8_t *uuid,
> + char *cfgbuf, int cfgsize, struct lkia *entries,
> + int max_entries, int *def_ent)
> +{
> + int rc;
"static char cfgbuf[CFG_BUF_SIZE];" should be here (without "static" I
suspect).
> +
> + rc = pxelinux_load_cfg(fn_ip, mac, uuid, cfgbuf, cfgsize);
> + if (rc < 0)
> + return rc;
And this:
cfgbuf[cfgbufsize - 1] = 0; /* Make sure it is NUL-terminated */
to make it clear what code actually cares about this nul termination.
> +
> + return pxelinux_parse_cfg(cfgbuf, rc, entries, max_entries, def_ent);
> +}
> diff --git a/lib/libnet/pxelinux.h b/lib/libnet/pxelinux.h
> new file mode 100644
> index 0000000..9fd1b2f
> --- /dev/null
> +++ b/lib/libnet/pxelinux.h
> @@ -0,0 +1,33 @@
> +/*****************************************************************************
> + * Definitions for pxelinux-style config file support
> + *
> + * Copyright 2018 Red Hat, Inc.
> + *
> + * This program and the accompanying materials
> + * are made available under the terms of the BSD License
> + * which accompanies this distribution, and is available at
> + * http://www.opensource.org/licenses/bsd-license.php
> + *
> + * Contributors:
> + * Thomas Huth, Red Hat Inc. - initial implementation
> + *****************************************************************************/
> +
> +#ifndef LIBNET_PXELINUX_H
> +#define LIBNET_PXELINUX_H
> +
> +/* This structure holds the data from one pxelinux.cfg file entry */
> +struct lkia {
The name "lkia" is funny, does some other pxelinux implementation use it?
:) "pxe_cfg_entry" would make more sense imho.
> + const char *label;
> + const char *kernel;
> + const char *initrd;
> + const char *append;
> +};
> +
> +int pxelinux_parse_cfg(char *cfg, int cfgsize, struct lkia *entries,
> + int max_entries, int *def_ent);
> +int pxelinux_load_parse_cfg(filename_ip_t *fn_ip, uint8_t *mac, uint8_t *uuid,
> + char *cfgbuf, int cfgsize, struct lkia *entries,
> + int max_entries, int *def_ent);
> +
> +
> +#endif
>
--
Alexey
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