From bbb4c4323a4d9cb5ca04db904aa3050a7586839a Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 4 Oct 2018 14:27:55 +0100 Subject: dns: Allow the dns resolver to retrieve a server set Allow the DNS resolver to retrieve a set of servers and their associated addresses, ports, preference and weight ratings. In terms of communication with userspace, "srv=1" is added to the callout string (the '1' indicating the maximum data version supported by the kernel) to ask the userspace side for this. If the userspace side doesn't recognise it, it will ignore the option and return the usual text address list. If the userspace side does recognise it, it will return some binary data that begins with a zero byte that would cause the string parsers to give an error. The second byte contains the version of the data in the blob (this may be between 1 and the version specified in the callout data). The remainder of the payload is version-specific. In version 1, the payload looks like (note that this is packed): u8 Non-string marker (ie. 0) u8 Content (0 => Server list) u8 Version (ie. 1) u8 Source (eg. DNS_RECORD_FROM_DNS_SRV) u8 Status (eg. DNS_LOOKUP_GOOD) u8 Number of servers foreach-server { u16 Name length (LE) u16 Priority (as per SRV record) (LE) u16 Weight (as per SRV record) (LE) u16 Port (LE) u8 Source (eg. DNS_RECORD_FROM_NSS) u8 Status (eg. DNS_LOOKUP_GOT_NOT_FOUND) u8 Protocol (eg. DNS_SERVER_PROTOCOL_UDP) u8 Number of addresses char[] Name (not NUL-terminated) foreach-address { u8 Family (AF_INET{,6}) union { u8[4] ipv4_addr u8[16] ipv6_addr } } } This can then be used to fetch a whole cell's VL-server configuration for AFS, for example. Signed-off-by: David Howells Signed-off-by: David S. Miller --- include/linux/dns_resolver.h | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'include/linux/dns_resolver.h') diff --git a/include/linux/dns_resolver.h b/include/linux/dns_resolver.h index 6ac3cad9aef1..34a744a1bafc 100644 --- a/include/linux/dns_resolver.h +++ b/include/linux/dns_resolver.h @@ -24,11 +24,9 @@ #ifndef _LINUX_DNS_RESOLVER_H #define _LINUX_DNS_RESOLVER_H -#ifdef __KERNEL__ +#include extern int dns_query(const char *type, const char *name, size_t namelen, const char *options, char **_result, time64_t *_expiry); -#endif /* KERNEL */ - #endif /* _LINUX_DNS_RESOLVER_H */ -- cgit v1.2.3-59-g8ed1b