--- name: "nfssvc" section: "2" platform: "linux" package: "freebsd-manpages" version: "6.0-5" release: "Debian 4.0 (Etch)" platforms: ["linux", "freebsd", "macos"] url: "https://new.carta.tech/nfssvc" --- # nfssvc(2) NFS services ## NAME **nfssvc** – NFS services ## LIBRARY Standard C Library (libc, -lc) ## SYNOPSIS **#include \** **#include \** **#include \** **#include \** **#include \** **#include \** *int*\ **nfssvc**(*int flags*, *void \*argstructp*); ## DESCRIPTION The **nfssvc**() system call is used by the NFS daemons to pass information into and out of the kernel and also to enter the kernel as a server daemon. The *flags* argument consists of several bits that show what action is to be taken once in the kernel and the *argstructp* points to one of three structures depending on which bits are set in flags. On the client side, [nfsiod(8)](/nfsiod/8.md) calls **nfssvc**() with the *flags* argument set to NFSSVC\_BIOD and *argstructp* set to NULL to enter the kernel as a block I/O server daemon. For NQNFS, [mount\_nfs(8)](/mount_nfs/8.md) calls **nfssvc**() with the NFSSVC\_MNTD flag, optionally or'd with the flags NFSSVC\_GOTAUTH and NFSSVC\_AUTHINFAIL along with a pointer to a ``` struct nfsd_cargs { char *ncd_dirp; /* Mount dir path */ uid_t ncd_authuid; /* Effective uid */ int ncd_authtype; /* Type of authenticator */ int ncd_authlen; /* Length of authenticator string */ u_char *ncd_authstr; /* Authenticator string */ int ncd_verflen; /* and the verifier */ u_char *ncd_verfstr; NFSKERBKEY_T ncd_key; /* Session key */ }; ``` structure. The initial call has only the NFSSVC\_MNTD flag set to specify service for the mount point. If the mount point is using Kerberos, then the [mount\_nfs(8)](/mount_nfs/8.md) utility will return from **nfssvc**() with *errno* == ENEEDAUTH whenever the client side requires an \`\`rcmd'' authentication ticket for the user. The [mount\_nfs(8)](/mount_nfs/8.md) utility will attempt to get the Kerberos ticket, and if successful will call **nfssvc**() with the flags NFSSVC\_MNTD and NFSSVC\_GOTAUTH after filling the ticket into the ncd\_authstr field and setting the ncd\_authlen and ncd\_authtype fields of the nfsd\_cargs structure. If [mount\_nfs(8)](/mount_nfs/8.md) failed to get the ticket, **nfssvc**() will be called with the flags NFSSVC\_MNTD, NFSSVC\_GOTAUTH and NFSSVC\_AUTHINFAIL to denote a failed authentication attempt. On the server side, **nfssvc**() is called with the flag NFSSVC\_NFSD and a pointer to a ``` struct nfsd_srvargs { struct nfsd *nsd_nfsd; /* Pointer to in kernel nfsd struct */ uid_t nsd_uid; /* Effective uid mapped to cred */ u_int32_t nsd_haddr; /* Ip address of client */ struct ucred nsd_cr; /* Cred. uid maps to */ int nsd_authlen; /* Length of auth string (ret) */ u_char *nsd_authstr; /* Auth string (ret) */ int nsd_verflen; /* and the verifier */ u_char *nsd_verfstr; struct timeval nsd_timestamp; /* timestamp from verifier */ u_int32_t nsd_ttl; /* credential ttl (sec) */ NFSKERBKEY_T nsd_key; /* Session key */ }; ``` to enter the kernel as an [nfsd(8)](/nfsd/8.md) daemon. Whenever an [nfsd(8)](/nfsd/8.md) daemon receives a Kerberos authentication ticket, it will return from **nfssvc**() with *errno* == ENEEDAUTH. The [nfsd(8)](/nfsd/8.md) utility will attempt to authenticate the ticket and generate a set of credentials on the server for the \`\`user id'' specified in the field nsd\_uid. This is done by first authenticating the Kerberos ticket and then mapping the Kerberos principal to a local name and getting a set of credentials for that user via [getpwnam(3)](/getpwnam/3.md) and [getgrouplist(3)](/getgrouplist/3.md). If successful, the [nfsd(8)](/nfsd/8.md) utility will call **nfssvc**() with the NFSSVC\_NFSD and NFSSVC\_AUTHIN flags set to pass the credential mapping in nsd\_cr into the kernel to be cached on the server socket for that client. If the authentication failed, [nfsd(8)](/nfsd/8.md) calls **nfssvc**() with the flags NFSSVC\_NFSD and NFSSVC\_AUTHINFAIL to denote an authentication failure. The master [nfsd(8)](/nfsd/8.md) server daemon calls **nfssvc**() with the flag NFSSVC\_ADDSOCK and a pointer to a ``` struct nfsd_args { int sock; /* Socket to serve */ caddr_t name; /* Client address for connection based sockets */ int namelen;/* Length of name */ }; ``` to pass a server side NFS socket into the kernel for servicing by the [nfsd(8)](/nfsd/8.md) daemons. ## RETURN VALUES Normally **nfssvc**() does not return unless the server is terminated by a signal when a value of 0 is returned. Otherwise, -1 is returned and the global variable *errno* is set to specify the error. ## ERRORS - \[ENEEDAUTH\] This special error value is really used for authentication support, particularly Kerberos, as explained above. - \[EPERM\] The caller is not the super-user. ## SEE ALSO [mount\_nfs(8)](/mount_nfs/8.md), [nfsd(8)](/nfsd/8.md), [nfsiod(8)](/nfsiod/8.md) ## HISTORY The **nfssvc**() system call first appeared in 4.4BSD. ## BUGS The **nfssvc**() system call is designed specifically for the NFS support daemons and as such is specific to their requirements. It should really return values to indicate the need for authentication support, since ENEEDAUTH is not really an error. Several fields of the argument structures are assumed to be valid and sometimes to be unchanged from a previous call, such that **nfssvc**() must be used with extreme care.