Re: klibc and logging

Alexander Viro (viro@math.psu.edu)
Tue, 13 Aug 2002 06:38:46 -0400 (EDT)


On Tue, 13 Aug 2002, Erik Andersen wrote:

> I would love to see an example of how to do an NFS mount w/o
> resorting to the C library at all. Plainly, having generic RPC
> code in the C library sucks, even if you trim it down. Having
> the entire NFS mount process live in application space, and not
> in the C library, is clearly a win....

See below - it's crud, but it works. Based of fs/nfs/nfsroot.c, moved
to userland with RPC done via syscalls and nothing else. Arguments are
passed via environment variables, replacing that with use of argv is
trivial... Other than syscalls uses: alarm(3), getenv(3), str... and
mem..., {s,}printf(3), htonl(3) and htons(3). About 4Kb of .text + .data
and aforementioned functions shouldn't add much to that.

Hardly usable as generic-purpose mount_nfs(8), but for nfsroot... I'd
prefer to have timeouts handled properly and code - cleaned up, but
other than that it should be usable.

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/utsname.h>
#include <netinet/in.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <stdlib.h>

/* Default path we try to mount. "%s" gets replaced by our IP address */
#define NFS_ROOT "/tftpboot/%s"
#define NFS_DEF_FILE_IO_BUFFER_SIZE 4096
#define NFS_MAXPATHLEN 1024
#define NFS_MNT_PROGRAM 100005
#define NFS_MNT_PORT 627
#define NFS_PROGRAM 100003
#define NFS_PORT 2049
#define NFS2_VERSION 2
#define NFS3_VERSION 3
#define NFS_MNT_PROGRAM 100005
#define NFS_MNT_VERSION 1
#define NFS_MNT3_VERSION 3
#define MNTPROC_MNT 1
#define MOUNTPROC3_MNT 1
#define RPC_PMAP_PROGRAM 100000
#define RPC_PMAP_VERSION 2
#define RPC_PMAP_PORT 111

#define NFS2_FHSIZE 32
#define NFS3_FHSIZE 64

#define RPC_VERSION 2

enum rpc_msg_type {
RPC_CALL = 0,
RPC_REPLY = 1
};

enum rpc_auth_flavor {
RPC_AUTH_NULL = 0,
RPC_AUTH_UNIX = 1,
RPC_AUTH_SHORT = 2,
RPC_AUTH_DES = 3,
RPC_AUTH_KRB = 4,
};

enum rpc_reply_stat {
RPC_MSG_ACCEPTED = 0,
RPC_MSG_DENIED = 1
};

#define NFS_MAXFHSIZE 64
struct nfs_fh {
unsigned short size;
unsigned char data[NFS_MAXFHSIZE];
};

struct nfs2_fh {
char data[NFS2_FHSIZE];
};

#define NFS_MOUNT_VERSION 4

struct nfs_mount_data {
int version;
int fd;
struct nfs2_fh old_root;
int flags;
int rsize;
int wsize;
int timeo;
int retrans;
int acregmin;
int acregmax;
int acdirmin;
int acdirmax;
struct sockaddr_in addr;
char hostname[256];
int namlen;
unsigned int bsize;
struct nfs_fh root;
};

#define NFS_MOUNT_SOFT 0x0001 /* 1 */
#define NFS_MOUNT_INTR 0x0002 /* 1 */
#define NFS_MOUNT_SECURE 0x0004 /* 1 */
#define NFS_MOUNT_POSIX 0x0008 /* 1 */
#define NFS_MOUNT_NOCTO 0x0010 /* 1 */
#define NFS_MOUNT_NOAC 0x0020 /* 1 */
#define NFS_MOUNT_TCP 0x0040 /* 2 */
#define NFS_MOUNT_VER3 0x0080 /* 3 */
#define NFS_MOUNT_KERBEROS 0x0100 /* 3 */
#define NFS_MOUNT_NONLM 0x0200 /* 3 */
#define NFS_MOUNT_BROKEN_SUID 0x0400 /* 4 */
#define NFS_MOUNT_FLAGMASK 0xFFFF

static char nfs_root_name[256];
static u_int32_t root_server_addr;
static char root_server_path[256];

/* Address of NFS server */
static u_int32_t servaddr;

/* Name of directory to mount */
static char nfs_path[NFS_MAXPATHLEN];

/* NFS-related data */
static struct nfs_mount_data nfs_data = {
.version = NFS_MOUNT_VERSION,
.flags = NFS_MOUNT_NONLM, /* No lockd in nfs root yet */
.rsize = NFS_DEF_FILE_IO_BUFFER_SIZE,
.wsize = NFS_DEF_FILE_IO_BUFFER_SIZE,
.bsize = 0,
.timeo = 7,
.retrans = 3,
.acregmin = 3,
.acregmax = 60,
.acdirmin = 30,
.acdirmax = 60,
};
static int nfs_port = -1;
static int mount_port;

/***************************************************************************

Parsing of options

***************************************************************************/

/*
* The following integer options are recognized
*/
static struct nfs_int_opts {
char *name;
int *val;
} root_int_opts[] = {
{ "port", &nfs_port },
{ "rsize", &nfs_data.rsize },
{ "wsize", &nfs_data.wsize },
{ "timeo", &nfs_data.timeo },
{ "retrans", &nfs_data.retrans },
{ "acregmin", &nfs_data.acregmin },
{ "acregmax", &nfs_data.acregmax },
{ "acdirmin", &nfs_data.acdirmin },
{ "acdirmax", &nfs_data.acdirmax },
{ NULL, NULL }
};

/*
* And now the flag options
*/
static struct nfs_bool_opts {
char *name;
int and_mask;
int or_mask;
} root_bool_opts[] = {
{ "soft", ~NFS_MOUNT_SOFT, NFS_MOUNT_SOFT },
{ "hard", ~NFS_MOUNT_SOFT, 0 },
{ "intr", ~NFS_MOUNT_INTR, NFS_MOUNT_INTR },
{ "nointr", ~NFS_MOUNT_INTR, 0 },
{ "posix", ~NFS_MOUNT_POSIX, NFS_MOUNT_POSIX },
{ "noposix", ~NFS_MOUNT_POSIX, 0 },
{ "cto", ~NFS_MOUNT_NOCTO, 0 },
{ "nocto", ~NFS_MOUNT_NOCTO, NFS_MOUNT_NOCTO },
{ "ac", ~NFS_MOUNT_NOAC, 0 },
{ "noac", ~NFS_MOUNT_NOAC, NFS_MOUNT_NOAC },
{ "lock", ~NFS_MOUNT_NONLM, 0 },
{ "nolock", ~NFS_MOUNT_NONLM, NFS_MOUNT_NONLM },
#ifdef CONFIG_NFS_V3
{ "v2", ~NFS_MOUNT_VER3, 0 },
{ "v3", ~NFS_MOUNT_VER3, NFS_MOUNT_VER3 },
#endif
{ "udp", ~NFS_MOUNT_TCP, 0 },
{ "tcp", ~NFS_MOUNT_TCP, NFS_MOUNT_TCP },
{ "broken_suid",~NFS_MOUNT_BROKEN_SUID, NFS_MOUNT_BROKEN_SUID },
{ NULL, 0, 0 }
};
/*
* Parse option string.
*/
static void root_nfs_parse(char *name, char *buf)
{
char *options, *val, *cp;

if ((options = strchr(name, ','))) {
*options++ = 0;
cp = strtok(options, ",");
while (cp) {
if ((val = strchr(cp, '='))) {
struct nfs_int_opts *opts = root_int_opts;
*val++ = '\0';
while (opts->name && strcmp(opts->name, cp))
opts++;
if (opts->name)
*(opts->val) = (int) strtoul(val, NULL, 10);
} else {
struct nfs_bool_opts *opts = root_bool_opts;
while (opts->name && strcmp(opts->name, cp))
opts++;
if (opts->name) {
nfs_data.flags &= opts->and_mask;
nfs_data.flags |= opts->or_mask;
}
}
cp = strtok(NULL, ",");
}
}
if (name[0] && strcmp(name, "default")) {
strncpy(buf, name, NFS_MAXPATHLEN-1);
buf[NFS_MAXPATHLEN-1] = 0;
}
}

/*
* Prepare the NFS data structure and parse all options.
*/
static int root_nfs_name(char *name)
{
char buf[NFS_MAXPATHLEN];
struct utsname uname_buf;

/* Set some default values */
strcpy(buf, NFS_ROOT);

/* Process options received from the remote server */
root_nfs_parse(root_server_path, buf);

/* Override them by options set on kernel command-line */
root_nfs_parse(name, buf);

uname(&uname_buf);
if (strlen(buf) + strlen(uname_buf.nodename) > NFS_MAXPATHLEN) {
printf("nfsroot: Pathname for remote directory too long.\n");
return -1;
}
sprintf(nfs_path, buf, uname_buf.nodename);

return 1;
}

/***************************************************************************

Routines to actually mount the root directory

***************************************************************************/

/*
* Construct sockaddr_in from address and port number.
*/
static inline void
set_sockaddr(struct sockaddr_in *sin, u_int32_t addr, u_int16_t port)
{
memset(sin, 0, sizeof(*sin));
sin->sin_family = AF_INET;
sin->sin_addr.s_addr = addr;
sin->sin_port = port;
}

/*
* Extremely crude RPC-over-UDP call. We get an already encoded request
* to pass, we do that and put the reply into buffer. That (and callers
* below - getport, getfh2 and getfh3) should be replaced with proper
* librpc use. Now, if we only had one that wasn't bloated as a dead
* gnu that had lied for a while under the sun...
*/

static u_int32_t XID;
static int flag;
static void timeout(int n)
{
flag = 1;
}
static int do_call(struct sockaddr_in *sin, u_int32_t msg[], u_int32_t rmsg[],
u_int32_t len, u_int32_t rlen)
{
struct sockaddr_in from;
int slen = sizeof(struct sockaddr_in);
struct timeval tv = {1, 0};
int n;
int fd;

signal(SIGALRM, timeout);
fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (fd < 0)
goto Esocket;
setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, (void*)&tv, sizeof(tv));
len *= 4;
if (sendto(fd, msg, len, 0, (struct sockaddr *)sin, slen)!=len)
goto Esend;
setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, (void*)&tv, sizeof(tv));
alarm(0);
flag = 0;
alarm(5);
rlen *= 4;
do {
slen = sizeof(from);
n = recvfrom(fd, rmsg, rlen, 0, (struct sockaddr*)&from, &slen);
if (flag || n < 0)
goto Erecv;
} while (memcmp(&from, sin, sizeof(from)) || rmsg[0] != msg[0]);

if (n < 6*4 || n % 4 || ntohl(rmsg[1]) != 1 || rmsg[2] ||
rmsg[3] || rmsg[4] || rmsg[5])
goto Einval;
alarm(0);
close(fd);
return n / 4 - 6;

Esend: printf("rpc: write failed\n");
goto out;
Erecv: printf("rpc: read failed\n");
goto out;
Einval: printf("rpc: invalid response\n");
goto out;
Esocket:printf("rpc: can't create socket\n");
return -1;
out:
alarm(0);
close(fd);
return -1;
}

enum {
PMAP_GETPORT = 3
};

static void do_header(u_int32_t msg[], u_int32_t prog, u_int32_t vers, u_int32_t proc)
{
msg[0] = XID++;
msg[1] = htonl(RPC_CALL);
msg[2] = htonl(RPC_VERSION);
msg[3] = htonl(prog);
msg[4] = htonl(vers);
msg[5] = htonl(proc);
msg[6] = htonl(RPC_AUTH_NULL);
msg[7] = htonl(0);
msg[8] = htonl(RPC_AUTH_NULL);
msg[9] = htonl(0);
}

static int getport(u_int32_t prog, u_int32_t vers, u_int32_t prot)
{
struct sockaddr_in sin;
unsigned msg[14];
unsigned rmsg[7];
int n;
set_sockaddr(&sin, servaddr, htons(RPC_PMAP_PORT));
do_header(msg, RPC_PMAP_PROGRAM, RPC_PMAP_VERSION, PMAP_GETPORT);
msg[10] = htonl(prog);
msg[11] = htonl(vers);
msg[12] = htonl(prot);
msg[13] = htonl(0);
n = do_call(&sin, msg, rmsg, 14, 7);
if (n <= 0)
return -1;
else
return ntohl(rmsg[6]);
}

static int getfh2(void)
{
struct sockaddr_in sin;
unsigned msg[10+1+256/4];
unsigned rmsg[6 + 1 + NFS2_FHSIZE/4];
int n;
int len = strlen(nfs_path);
set_sockaddr(&sin, servaddr, mount_port);

if (len > 255) {
printf("nfsroot: pathname is too long");
return -1;
}
memset(msg, 0, sizeof(msg));
do_header(msg, NFS_MNT_PROGRAM, NFS_MNT_VERSION, MNTPROC_MNT);
msg[10] = htonl(len);
strcpy((char*)&msg[11], nfs_path);
n = do_call(&sin, msg, rmsg, 11 + (len + 3)/4, 7 + NFS2_FHSIZE/4);
if (n < 0)
return -1;
if (n != NFS2_FHSIZE/4 + 1)
goto Esize;
if (rmsg[6]) {
printf("nfsroot: mountd returned an error (%d)",htonl(rmsg[6]));
return -1;
}
nfs_data.root.size = NFS2_FHSIZE;
memcpy(nfs_data.root.data, &rmsg[7], NFS2_FHSIZE);
return 0;
Esize:
printf("nfsroot: bad fhandle size");
return -1;
}

static int getfh3(void)
{
struct sockaddr_in sin;
unsigned msg[10+1+256/4];
unsigned rmsg[6 + 1 + 1 + NFS3_FHSIZE/4];
int n;
int len = strlen(nfs_path);
int size;
set_sockaddr(&sin, servaddr, mount_port);

if (len > 255) {
printf("nfsroot: pathname is too long");
return -1;
}
memset(msg, 0, sizeof(msg));
do_header(msg, NFS_MNT_PROGRAM, NFS_MNT3_VERSION, MOUNTPROC3_MNT);
msg[10] = htonl(len);
strcpy((char*)&msg[11], nfs_path);
n = do_call(&sin, msg, rmsg, 11 + (len + 3)/4, 8 + NFS3_FHSIZE/4);
if (n < 0)
return -1;
if (n <= 2)
goto Esize;
if (rmsg[6]) {
printf("nfsroot: mountd returned an error (%d)",htonl(rmsg[6]));
return -1;
}
size = ntohl(rmsg[7]);
if (size > NFS3_FHSIZE || n != 2 + size/4)
goto Esize;
nfs_data.root.size = size;
memcpy(nfs_data.root.data, &rmsg[8], size);
return 0;
Esize:
printf("nfsroot: bad fhandle size");
return -1;
}

/*
* Use portmapper to find mountd and nfsd port numbers if not overriden
* by the user. Use defaults if portmapper is not available.
* XXX: Is there any nfs server with no portmapper?
*/
static int root_nfs_ports(void)
{
int port;
int nfsd_ver, mountd_ver;
int proto;

if (nfs_data.flags & NFS_MOUNT_VER3) {
nfsd_ver = NFS3_VERSION;
mountd_ver = NFS_MNT3_VERSION;
} else {
nfsd_ver = NFS2_VERSION;
mountd_ver = NFS_MNT_VERSION;
}

proto = (nfs_data.flags & NFS_MOUNT_TCP) ? IPPROTO_TCP : IPPROTO_UDP;

if (nfs_port < 0) {
if ((port = getport(NFS_PROGRAM, nfsd_ver, proto)) < 0) {
printf("nfsroot: Unable to get nfsd port "
"number from server, using default\n");
port = NFS_PORT;
}
nfs_port = htons(port);
printf("nfsroot: Portmapper on server returned %d "
"as nfsd port\n", port);
}

if ((port = getport(NFS_MNT_PROGRAM, mountd_ver, proto)) < 0) {
printf("nfsroot: Unable to get mountd port "
"number from server, using default\n");
port = NFS_MNT_PORT;
}
mount_port = htons(port);
printf("nfsroot: mountd port is %d\n", port);

return 0;
}

int main()
{
unsigned char *p;
struct timeval tv;
char *s;

s = getenv("root_server_addr");
if (s)
root_server_addr = strtoul(s, NULL, 10);
s = getenv("root_server_path");
if (s)
strncpy(root_server_path, s, 255);
s = getenv("nfs_root_name");
if (s)
strncpy(nfs_root_name, s, 255);

/*
* Decode the root directory path name and NFS options from
* the kernel command line. This has to go here in order to
* be able to use the client IP address for the remote root
* directory (necessary for pure RARP booting).
*/
if (root_nfs_name(nfs_root_name) < 0)
return 0;
if ((servaddr = root_server_addr) == INADDR_NONE) {
printf("nfsroot: No NFS server available, giving up.\n");
return 0;
}

p = (char *) &servaddr;
sprintf(nfs_data.hostname, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);

#ifdef NFSROOT_DEBUG
printf("nfsroot: Mounting %s on server %s as root\n",
nfs_path, nfs_data.hostname);
printf("nfsroot: rsize = %d, wsize = %d, timeo = %d, retrans = %d\n",
nfs_data.rsize, nfs_data.wsize, nfs_data.timeo, nfs_data.retrans);
printf("nfsroot: acreg (min,max) = (%d,%d), acdir (min,max) = (%d,%d)\n",
nfs_data.acregmin, nfs_data.acregmax,
nfs_data.acdirmin, nfs_data.acdirmax);
printf("nfsroot: nfsd port = %d, mountd port = %d, flags = %08x\n",
nfs_port, mount_port, nfs_data.flags);
#endif

gettimeofday(&tv, NULL);
XID = (tv.tv_sec << 15) ^ tv.tv_usec;

if (root_nfs_ports() < 0)
return 0;
if (nfs_data.flags & NFS_MOUNT_VER3) {
if (getfh3())
return 0;
} else {
if (getfh2())
return 0;
}
set_sockaddr((struct sockaddr_in *) &nfs_data.addr, servaddr, nfs_port);
return mount("/dev/root", "/mnt", "nfs", 0, &nfs_data) == 0;
}

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/