[SLOF] [PATCH v2 06/11] libnet: Add functions for downloading and parsing pxelinux.cfg files

[Thomas Huth]

On 25.05.2018 08:45, Alexey Kardashevskiy wrote:
> 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];
>> +	char *slash;
>> +
>> +	cfgbuf[cfgbufsize - 1] = 0;  /* Make sure it is NUL-terminated */
>> +
>> +	/* 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/");
>> +	}
>> +
>> +	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;
>> +		}
>> +	}
> 
> 
> This belongs to 11/11. Also, this UUID comes from QEMU's system-id DT
> property which is formatted as xxxx-xx-xx-xx-xxxxxx (UUID_FMT in QEMU)
> which is exactly the same as above, cannot you just use the plain string
> from the property and avoid parsing/sprintf?

Again, the answer is the s390-ccw bios: There you get the UUID in binary
form, not in string form. But ok, I can also convert the binary UUID to
a string in the s390-ccw bios already and always use a string in
pxelinux.c, so I'll try to do that in the next version of the patch.

 Thomas