/*      $OpenBSD: svc_udp.c,v 1.27 2022/02/14 03:38:59 guenther Exp $ */

/*
 * Copyright (c) 2010, Oracle America, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 *       copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials
 *       provided with the distribution.
 *     * Neither the name of the "Oracle America, Inc." nor the names of its
 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 *   FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 *   COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 *   INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 *   DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 *   GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 *   WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 *   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * svc_udp.c,
 * Server side for UDP/IP based RPC.  (Does some caching in the hopes of
 * achieving execute-at-most-once semantics.)
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <rpc/rpc.h>
#include <sys/socket.h>
#include <stdint.h>
#include <errno.h>
#include <unistd.h>


#define rpc_buffer(xprt) ((xprt)->xp_p1)
#define MAX(a, b)     ((a > b) ? a : b)

static bool_t           svcudp_recv(SVCXPRT *, struct rpc_msg *);
static enum xprt_stat   svcudp_stat(SVCXPRT *);
static bool_t           svcudp_getargs(SVCXPRT *, xdrproc_t, caddr_t);
static bool_t           svcudp_reply(SVCXPRT *, struct rpc_msg *);
static bool_t           svcudp_freeargs(SVCXPRT *, xdrproc_t, caddr_t);
static void             svcudp_destroy(SVCXPRT *);
static void             cache_set(SVCXPRT *, u_long);
static int              cache_get(SVCXPRT *, struct rpc_msg *, char **,
                            u_long *);

static const struct xp_ops svcudp_op = {
        svcudp_recv,
        svcudp_stat,
        svcudp_getargs,
        svcudp_reply,
        svcudp_freeargs,
        svcudp_destroy
};

/*
 * kept in xprt->xp_p2
 */
struct svcudp_data {
        u_int   su_iosz;        /* byte size of send.recv buffer */
        u_long  su_xid;         /* transaction id */
        XDR     su_xdrs;        /* XDR handle */
        char    su_verfbody[MAX_AUTH_BYTES];    /* verifier body */
        char *  su_cache;       /* cached data, NULL if no cache */
};
#define su_data(xprt)   ((struct svcudp_data *)(xprt->xp_p2))

/*
 * Usage:
 *      xprt = svcudp_create(sock);
 *
 * If sock<0 then a socket is created, else sock is used.
 * If the socket, sock is not bound to a port then svcudp_create
 * binds it to an arbitrary port.  In any (successful) case,
 * xprt->xp_sock is the registered socket number and xprt->xp_port is the
 * associated port number.
 * Once *xprt is initialized, it is registered as a transporter;
 * see (svc.h, xprt_register).
 * The routines returns NULL if a problem occurred.
 */
SVCXPRT *
svcudp_bufcreate(int sock, u_int sendsz, u_int recvsz)
{
        bool_t madesock = FALSE;
        SVCXPRT *xprt;
        struct svcudp_data *su;
        struct sockaddr_in addr;
        socklen_t len = sizeof(struct sockaddr_in);

        if (sock == RPC_ANYSOCK) {
                if ((sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)
                        return (NULL);
                madesock = TRUE;
        }
        memset(&addr, 0, sizeof (addr));
        addr.sin_len = sizeof(struct sockaddr_in);
        addr.sin_family = AF_INET;
        if (bindresvport(sock, &addr)) {
                addr.sin_port = 0;
                (void)bind(sock, (struct sockaddr *)&addr, len);
        }
        if (getsockname(sock, (struct sockaddr *)&addr, &len) != 0) {
                if (madesock)
                        (void)close(sock);
                return (NULL);
        }
        xprt = malloc(sizeof(SVCXPRT));
        if (xprt == NULL) {
                if (madesock)
                        (void)close(sock);
                return (NULL);
        }
        su = malloc(sizeof(*su));
        if (su == NULL) {
                if (madesock)
                        (void)close(sock);
                free(xprt);
                return (NULL);
        }
        su->su_iosz = ((MAX(sendsz, recvsz) + 3) / 4) * 4;
        if ((rpc_buffer(xprt) = malloc(su->su_iosz)) == NULL) {
                if (madesock)
                        (void)close(sock);
                free(xprt);
                free(su);
                return (NULL);
        }
        xdrmem_create(&(su->su_xdrs), rpc_buffer(xprt), su->su_iosz,
            XDR_DECODE);
        su->su_cache = NULL;
        xprt->xp_p2 = (caddr_t)su;
        xprt->xp_verf.oa_base = su->su_verfbody;
        xprt->xp_ops = &svcudp_op;
        xprt->xp_port = ntohs(addr.sin_port);
        xprt->xp_sock = sock;
        if (__xprt_register(xprt) == 0) {
                if (madesock)
                        (void)close(sock);
                free(rpc_buffer(xprt));
                free(xprt);
                free(su);
                return (NULL);
        }
        return (xprt);
}
DEF_WEAK(svcudp_bufcreate);

SVCXPRT *
svcudp_create(int sock)
{

        return(svcudp_bufcreate(sock, UDPMSGSIZE, UDPMSGSIZE));
}
DEF_WEAK(svcudp_create);

static enum xprt_stat
svcudp_stat(SVCXPRT *xprt)
{

        return (XPRT_IDLE); 
}

static bool_t
svcudp_recv(SVCXPRT *xprt, struct rpc_msg *msg)
{
        struct svcudp_data *su = su_data(xprt);
        XDR *xdrs = &(su->su_xdrs);
        int rlen;
        char *reply;
        u_long replylen;

    again:
        xprt->xp_addrlen = sizeof(struct sockaddr_in);
        rlen = recvfrom(xprt->xp_sock, rpc_buffer(xprt), (int) su->su_iosz,
            0, (struct sockaddr *)&(xprt->xp_raddr), &(xprt->xp_addrlen));
        if (rlen == -1 && errno == EINTR)
                goto again;
        if (rlen == -1 || rlen < 4*sizeof(u_int32_t))
                return (FALSE);
        xdrs->x_op = XDR_DECODE;
        XDR_SETPOS(xdrs, 0);
        if (! xdr_callmsg(xdrs, msg))
                return (FALSE);
        su->su_xid = msg->rm_xid;
        if (su->su_cache != NULL) {
                if (cache_get(xprt, msg, &reply, &replylen)) {
                        (void) sendto(xprt->xp_sock, reply, (int) replylen, 0,
                            (struct sockaddr *) &xprt->xp_raddr,
                            xprt->xp_addrlen);
                        return (TRUE);
                }
        }
        return (TRUE);
}

static bool_t
svcudp_reply(SVCXPRT *xprt, struct rpc_msg *msg)
{
        struct svcudp_data *su = su_data(xprt);
        XDR *xdrs = &(su->su_xdrs);
        int slen;
        bool_t stat = FALSE;

        xdrs->x_op = XDR_ENCODE;
        XDR_SETPOS(xdrs, 0);
        msg->rm_xid = su->su_xid;
        if (xdr_replymsg(xdrs, msg)) {
                slen = (int)XDR_GETPOS(xdrs);
                if (sendto(xprt->xp_sock, rpc_buffer(xprt), slen, 0,
                    (struct sockaddr *)&(xprt->xp_raddr), xprt->xp_addrlen)
                    == slen) {
                        stat = TRUE;
                        if (su->su_cache && slen >= 0) {
                                cache_set(xprt, (u_long) slen);
                        }
                }
        }
        return (stat);
}

static bool_t
svcudp_getargs(SVCXPRT *xprt, xdrproc_t xdr_args, caddr_t args_ptr)
{

        return ((*xdr_args)(&(su_data(xprt)->su_xdrs), args_ptr));
}

static bool_t
svcudp_freeargs(SVCXPRT *xprt, xdrproc_t xdr_args, caddr_t args_ptr)
{
        XDR *xdrs = &(su_data(xprt)->su_xdrs);

        xdrs->x_op = XDR_FREE;
        return ((*xdr_args)(xdrs, args_ptr));
}

static void
svcudp_destroy(SVCXPRT *xprt)
{
        struct svcudp_data *su = su_data(xprt);

        xprt_unregister(xprt);
        if (xprt->xp_sock != -1)
                (void)close(xprt->xp_sock);
        xprt->xp_sock = -1;
        XDR_DESTROY(&(su->su_xdrs));
        mem_free(rpc_buffer(xprt), su->su_iosz);
        mem_free((caddr_t)su, sizeof(struct svcudp_data));
        mem_free((caddr_t)xprt, sizeof(SVCXPRT));
}

/*
 * Fifo cache for udp server
 * Copies pointers to reply buffers into fifo cache
 * Buffers are sent again if retransmissions are detected.
 */

#define SPARSENESS 4    /* 75% sparse */

/*
 * An entry in the cache
 */
typedef struct cache_node *cache_ptr;
struct cache_node {
        /*
         * Index into cache is xid, proc, vers, prog and address
         */
        u_long cache_xid;
        u_long cache_proc;
        u_long cache_vers;
        u_long cache_prog;
        struct sockaddr_in cache_addr;
        /*
         * The cached reply and length
         */
        char * cache_reply;
        u_long cache_replylen;
        /*
         * Next node on the list, if there is a collision
         */
        cache_ptr cache_next;   
};

/*
 * The entire cache
 */
struct udp_cache {
        u_long uc_size;         /* size of cache */
        cache_ptr *uc_entries;  /* hash table of entries in cache */
        cache_ptr *uc_fifo;     /* fifo list of entries in cache */
        u_long uc_nextvictim;   /* points to next victim in fifo list */
        u_long uc_prog;         /* saved program number */
        u_long uc_vers;         /* saved version number */
        u_long uc_proc;         /* saved procedure number */
        struct sockaddr_in uc_addr; /* saved caller's address */
};


/*
 * the hashing function
 */
#define CACHE_LOC(transp, xid)  \
 (xid % (SPARSENESS*((struct udp_cache *) su_data(transp)->su_cache)->uc_size)) 


/*
 * Enable use of the cache. 
 * Note: there is no disable.
 */
int
svcudp_enablecache(SVCXPRT *transp, u_long size)
{
        struct svcudp_data *su = su_data(transp);
        struct udp_cache *uc;

        if (su->su_cache != NULL)
                return(0);      
        uc = malloc(sizeof(*uc));
        if (uc == NULL)
                return(0);
        uc->uc_size = size;
        uc->uc_nextvictim = 0;
        if (size > SIZE_MAX / (sizeof(cache_ptr) * SPARSENESS) ||
            (uc->uc_entries = calloc(size, sizeof(cache_ptr) * SPARSENESS)) == NULL) {
                free(uc);
                return(0);
        }
        uc->uc_fifo = calloc(sizeof(cache_ptr), size);
        if (uc->uc_fifo == NULL) {
                free(uc->uc_entries);
                free(uc);
                return(0);
        }
        su->su_cache = (char *) uc;
        return(1);
}


/*
 * Set an entry in the cache
 */
static void
cache_set(SVCXPRT *xprt, u_long replylen)
{
        cache_ptr victim;       
        cache_ptr *vicp;
        struct svcudp_data *su = su_data(xprt);
        struct udp_cache *uc = (struct udp_cache *) su->su_cache;
        u_int loc;
        char *newbuf;

        /*
         * Find space for the new entry, either by
         * reusing an old entry, or by mallocing a new one
         */
        victim = uc->uc_fifo[uc->uc_nextvictim];
        if (victim != NULL) {
                loc = CACHE_LOC(xprt, victim->cache_xid);
                for (vicp = &uc->uc_entries[loc]; 
                  *vicp != NULL && *vicp != victim; 
                  vicp = &(*vicp)->cache_next) 
                                ;
                if (*vicp == NULL) {
                        return;
                }
                *vicp = victim->cache_next;     /* remote from cache */
                newbuf = victim->cache_reply;
        } else {
                victim = malloc(sizeof(struct cache_node));
                if (victim == NULL) {
                        return;
                }
                newbuf = malloc(su->su_iosz);
                if (newbuf == NULL) {
                        free(victim);
                        return;
                }
        }

        /*
         * Store it away
         */
        victim->cache_replylen = replylen;
        victim->cache_reply = rpc_buffer(xprt);
        rpc_buffer(xprt) = newbuf;
        xdrmem_create(&(su->su_xdrs), rpc_buffer(xprt), su->su_iosz, XDR_ENCODE);
        victim->cache_xid = su->su_xid;
        victim->cache_proc = uc->uc_proc;
        victim->cache_vers = uc->uc_vers;
        victim->cache_prog = uc->uc_prog;
        victim->cache_addr = uc->uc_addr;
        loc = CACHE_LOC(xprt, victim->cache_xid);
        victim->cache_next = uc->uc_entries[loc];       
        uc->uc_entries[loc] = victim;
        uc->uc_fifo[uc->uc_nextvictim++] = victim;
        uc->uc_nextvictim %= uc->uc_size;
}

/*
 * Try to get an entry from the cache
 * return 1 if found, 0 if not found
 */
static int
cache_get(SVCXPRT *xprt, struct rpc_msg *msg, char **replyp, u_long *replylenp)
{
        u_int loc;
        cache_ptr ent;
        struct svcudp_data *su = su_data(xprt);
        struct udp_cache *uc = (struct udp_cache *) su->su_cache;

#       define EQADDR(a1, a2)   (memcmp(&a1, &a2, sizeof(a1)) == 0)

        loc = CACHE_LOC(xprt, su->su_xid);
        for (ent = uc->uc_entries[loc]; ent != NULL; ent = ent->cache_next) {
                if (ent->cache_xid == su->su_xid &&
                  ent->cache_proc == uc->uc_proc &&
                  ent->cache_vers == uc->uc_vers &&
                  ent->cache_prog == uc->uc_prog &&
                  EQADDR(ent->cache_addr, uc->uc_addr)) {
                        *replyp = ent->cache_reply;
                        *replylenp = ent->cache_replylen;
                        return(1);
                }
        }
        /*
         * Failed to find entry
         * Remember a few things so we can do a set later
         */
        uc->uc_proc = msg->rm_call.cb_proc;
        uc->uc_vers = msg->rm_call.cb_vers;
        uc->uc_prog = msg->rm_call.cb_prog;
        uc->uc_addr = xprt->xp_raddr;
        return(0);
}