[syslinux] Domain name search path use during PXE booting
Stephen Bleazard
sbleazard at janestreet.com
Thu Jan 7 02:25:38 PST 2016
Currently it appears that when PXE booting the domain search option is ignored
and only the domain name option used for name resolution.
The following patch adds support for domain search path usage when PXE
booting:
- adds parsing of the DHCP domain search option (119)
- When resolving names via dns_resolv uses the search path if there's no
dot in the name.
- Reverts to the previous behaviour in the absence of a search path, if
the name contains a dot or if no addresses are found when searching the
domain search path.
Steve Bleazard
--
diff -upr syslinux-6.03.orig/core/fs/pxe/dhcp_option.c syslinux-6.03/core/fs/pxe/dhcp_option.c
--- syslinux-6.03.orig/core/fs/pxe/dhcp_option.c 2014-10-06 17:27:44.000000000 +0100
+++ syslinux-6.03/core/fs/pxe/dhcp_option.c 2016-01-04 07:58:18.158206039 +0000
@@ -7,6 +7,11 @@
#include "pxe.h"
char LocalDomain[256];
+/*
+ * DomainSearch contains a list of null terminated domain names
+ * An empty string terminates the list
+ */
+char DomainSearch[257];
int over_load;
uint8_t uuid_type;
@@ -133,6 +138,135 @@ static void pxelinux_reboottime(const vo
DHCPMagic |= 8; /* Got reboot time */
}
+/*
+ * See RFC1035 section 4.1.3 for the format of the domain name as it's a compact format.
+ */
+static void domain_search(const void *data, int opt_len)
+{
+ const uint8_t *udata = (uint8_t *)data;
+ const uint8_t *inp = udata; /* in the buffer, does not follow pointers */
+ char *outp = DomainSearch; /* current location to output chars to */
+ char *endp = DomainSearch; /* end of the last completed domain string */
+ const uint8_t *cpp; /* copy pointer used to follow pointers */
+ int pcount; /* number of pointers visited in current point copy */
+ int len;
+ enum { START, LABEL, ADD_LABEL, ADD_DOT, CP_LEN_1, CP_LABEL, CP_ADD_LABEL,
+ CP_ADD_DOT, CP_LEN_2, FINISH, END } state, postcpstate;
+
+ state = START;
+ while (state != END) {
+ switch (state) {
+ case START:
+ cpp = udata;
+ state = LABEL;
+ break;
+
+ case LABEL:
+ len = *inp++;
+ if ((len & 0xc0) == 0xc0) { /* pointer */
+ state = CP_LEN_1;
+ len = (len & ~0xc0) << 8;
+ pcount = 0;
+ } else if (len > 0) { /* label length */
+ state = ADD_LABEL;
+ } else { /* end of string - terminate the string */
+ if (outp - endp > 0) { /* only if not a null string */
+ outp--; /* backup over the '.' */
+ *outp++ = '\0';
+ }
+ endp = outp;
+ }
+ break;
+
+ case ADD_LABEL:
+ *outp++ = (char)*inp++;
+ if (--len <= 0)
+ state = ADD_DOT;
+ break;
+
+ case ADD_DOT:
+ *outp++ = '.';
+ state = LABEL;
+ break;
+
+ case CP_LEN_1:
+ state = CP_LABEL;
+ len += *inp++;
+ cpp = udata + len;
+ postcpstate = LABEL;
+ /*
+ * edge condition - the last entry in the buffer is a pointer,
+ * - decrement inp to prevent overflow detection
+ * - set post pointer copying state to FINISH
+ */
+ if (inp >= udata + opt_len) {
+ inp--;
+ postcpstate = FINISH;
+ }
+ break;
+
+ case CP_LABEL:
+ len = *cpp++;
+ if ((len & 0xc0) == 0xc0) {
+ state = CP_LEN_2;
+ len = (len & ~0xc0) << 8;
+ } else if (len > 0) {
+ state = CP_ADD_LABEL;
+ } else {
+ /* terminate the string */
+ if (outp - endp > 0) { /* only if not a null string */
+ outp--; /* backup over the '.' */
+ *outp++ = '\0';
+ }
+ cpp = udata; /* prevent cpp going past end of buffer */
+ endp = outp;
+ state = postcpstate;
+ }
+ break;
+
+ case CP_LEN_2:
+ state = CP_LABEL;
+ len += *cpp++;
+ cpp = udata + len;
+ /*
+ * Detect pointer loops and exit pointer copying
+ */
+ if (++pcount >= 32) {
+ outp = endp; /* discard looping entry */
+ state = postcpstate;
+ }
+ break;
+
+ case CP_ADD_LABEL:
+ *outp++ = (char)*cpp++;
+ if (--len <= 0)
+ state = CP_ADD_DOT;
+ break;
+
+ case CP_ADD_DOT:
+ *outp++ = '.';
+ state = CP_LABEL;
+ break;
+
+ case FINISH:
+ state = END;
+ *endp = '\0';
+ break;
+ }
+
+ if (state != END) {
+ if (inp - udata >= opt_len)
+ state = FINISH;
+
+ if (cpp - udata >= opt_len)
+ state = FINISH;
+
+ if (outp - DomainSearch >= sizeof(DomainSearch) - 1)
+ state = FINISH;
+ }
+ }
+}
+
struct dhcp_options {
int opt_num;
@@ -150,6 +284,7 @@ static const struct dhcp_options dhcp_op
{61, client_identifier},
{67, bootfile_name},
{97, uuid_client_identifier},
+ {119, domain_search},
{209, pxelinux_configfile},
{210, pxelinux_pathprefix},
{211, pxelinux_reboottime}
@@ -222,6 +357,7 @@ void parse_dhcp_options(const void *opti
* boot_file - boot file name
* DNSServers - DNS server IPs
* LocalDomain - Local domain name
+ * DomainSearch - Domain search path
* MAC_len, MAC - Client identifier, if MAC_len == 0
*
*/
diff -upr syslinux-6.03.orig/core/fs/pxe/dnsresolv.c syslinux-6.03/core/fs/pxe/dnsresolv.c
--- syslinux-6.03.orig/core/fs/pxe/dnsresolv.c 2014-10-06 17:27:44.000000000 +0100
+++ syslinux-6.03/core/fs/pxe/dnsresolv.c 2015-11-26 16:09:27.904865172 +0000
@@ -93,6 +93,7 @@ __export uint32_t dns_resolv(const char
err_t err;
struct ip_addr ip;
char fullname[512];
+ char *p;
/*
* Return failure on an empty input... this can happen during
@@ -110,6 +111,16 @@ __export uint32_t dns_resolv(const char
if (!dns_getserver(0).addr)
return 0;
+ /* Do we have a domain search list */
+ if (!strchr(name, '.') && DomainSearch[0]) {
+ for (p = DomainSearch; *p != '\0'; p += strlen(p) + 1) {
+ snprintf(fullname, sizeof fullname, "%s.%s", name, p);
+ err = netconn_gethostbyname(fullname, &ip);
+ if (!err)
+ return ip.addr;
+ }
+ }
+
/* Is it a local (unqualified) domain name? */
if (!strchr(name, '.') && LocalDomain[0]) {
snprintf(fullname, sizeof fullname, "%s.%s", name, LocalDomain);
diff -upr syslinux-6.03.orig/core/fs/pxe/pxe.h syslinux-6.03/core/fs/pxe/pxe.h
--- syslinux-6.03.orig/core/fs/pxe/pxe.h 2014-10-06 17:27:44.000000000 +0100
+++ syslinux-6.03/core/fs/pxe/pxe.h 2015-11-26 07:54:01.516841867 +0000
@@ -169,6 +169,7 @@ extern uint32_t RebootTime;
extern char boot_file[];
extern char path_prefix[];
extern char LocalDomain[];
+extern char DomainSearch[];
extern uint32_t dns_server[];
--
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