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f6b7dc47c76970a60a54449e681d43f01cd27fe4
dnsmasq/src/forward.c
Simon Kelley f6b7dc47c7 import of dnsmasq-2.20.tar.gz
2012-01-05 17:31:11 +00:00

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/* dnsmasq is Copyright (c) 2000 - 2005 Simon Kelley
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 dated June, 1991.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
*/
/* Author's email: simon@thekelleys.org.uk */
#include "dnsmasq.h"
static struct frec *frec_list;
static struct frec *get_new_frec(time_t now);
static struct frec *lookup_frec(unsigned short id);
static struct frec *lookup_frec_by_sender(unsigned short id,
union mysockaddr *addr,
unsigned int crc);
static unsigned short get_id(void);
/* May be called more than once. */
void forward_init(int first)
{
struct frec *f;
if (first)
frec_list = NULL;
for (f = frec_list; f; f = f->next)
f->new_id = 0;
}
/* Send a UDP packet with it's source address set as "source"
unless nowild is true, when we just send it with the kernel default */
static void send_from(int fd, int nowild, char *packet, int len,
union mysockaddr *to, struct all_addr *source,
unsigned int iface)
{
struct msghdr msg;
struct iovec iov[1];
union {
struct cmsghdr align; /* this ensures alignment */
#if defined(IP_PKTINFO)
char control[CMSG_SPACE(sizeof(struct in_pktinfo))];
#elif defined(IP_SENDSRCADDR)
char control[CMSG_SPACE(sizeof(struct in_addr))];
#endif
#ifdef HAVE_IPV6
char control6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
#endif
} control_u;
iov[0].iov_base = packet;
iov[0].iov_len = len;
msg.msg_control = NULL;
msg.msg_controllen = 0;
msg.msg_flags = 0;
msg.msg_name = to;
msg.msg_namelen = sa_len(to);
msg.msg_iov = iov;
msg.msg_iovlen = 1;
if (!nowild)
{
struct cmsghdr *cmptr;
msg.msg_control = &control_u;
msg.msg_controllen = sizeof(control_u);
cmptr = CMSG_FIRSTHDR(&msg);
if (to->sa.sa_family == AF_INET)
{
#if defined(IP_PKTINFO)
struct in_pktinfo *pkt = (struct in_pktinfo *)CMSG_DATA(cmptr);
pkt->ipi_ifindex = 0;
pkt->ipi_spec_dst = source->addr.addr4;
msg.msg_controllen = cmptr->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
cmptr->cmsg_level = SOL_IP;
cmptr->cmsg_type = IP_PKTINFO;
#elif defined(IP_SENDSRCADDR)
struct in_addr *a = (struct in_addr *)CMSG_DATA(cmptr);
*a = source->addr.addr4;
msg.msg_controllen = cmptr->cmsg_len = CMSG_LEN(sizeof(struct in_addr));
cmptr->cmsg_level = IPPROTO_IP;
cmptr->cmsg_type = IP_SENDSRCADDR;
#endif
}
#ifdef HAVE_IPV6
else
{
struct in6_pktinfo *pkt = (struct in6_pktinfo *)CMSG_DATA(cmptr);
pkt->ipi6_ifindex = iface; /* Need iface for IPv6 to handle link-local addrs */
pkt->ipi6_addr = source->addr.addr6;
msg.msg_controllen = cmptr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
cmptr->cmsg_type = IPV6_PKTINFO;
cmptr->cmsg_level = IPV6_LEVEL;
}
#endif
}
retry:
if (sendmsg(fd, &msg, 0) == -1)
{
/* certain Linux kernels seem to object to setting the source address in the IPv6 stack
by returning EINVAL from sendmsg. In that case, try again without setting the
source address, since it will nearly alway be correct anyway. IPv6 stinks. */
if (errno == EINVAL && msg.msg_controllen)
{
msg.msg_controllen = 0;
goto retry;
}
if (retry_send())
goto retry;
}
}
static unsigned short search_servers(struct daemon *daemon, time_t now, struct all_addr **addrpp,
unsigned short qtype, char *qdomain, int *type, char **domain)
{
/* If the query ends in the domain in one of our servers, set
domain to point to that name. We find the largest match to allow both
domain.org and sub.domain.org to exist. */
unsigned int namelen = strlen(qdomain);
unsigned int matchlen = 0;
struct server *serv;
unsigned short flags = 0;
for (serv = daemon->servers; serv; serv=serv->next)
/* domain matches take priority over NODOTS matches */
if ((serv->flags & SERV_FOR_NODOTS) && *type != SERV_HAS_DOMAIN && !strchr(qdomain, '.'))
{
unsigned short sflag = serv->addr.sa.sa_family == AF_INET ? F_IPV4 : F_IPV6;
*type = SERV_FOR_NODOTS;
if (serv->flags & SERV_NO_ADDR)
flags = F_NXDOMAIN;
else if (serv->flags & SERV_LITERAL_ADDRESS)
{
if (sflag & qtype)
{
flags = sflag;
if (serv->addr.sa.sa_family == AF_INET)
*addrpp = (struct all_addr *)&serv->addr.in.sin_addr;
#ifdef HAVE_IPV6
else
*addrpp = (struct all_addr *)&serv->addr.in6.sin6_addr;
#endif
}
else if (!flags)
flags = F_NOERR;
}
}
else if (serv->flags & SERV_HAS_DOMAIN)
{
unsigned int domainlen = strlen(serv->domain);
if (namelen >= domainlen &&
hostname_isequal(qdomain + namelen - domainlen, serv->domain) &&
domainlen >= matchlen)
{
unsigned short sflag = serv->addr.sa.sa_family == AF_INET ? F_IPV4 : F_IPV6;
*type = SERV_HAS_DOMAIN;
*domain = serv->domain;
matchlen = domainlen;
if (serv->flags & SERV_NO_ADDR)
flags = F_NXDOMAIN;
else if (serv->flags & SERV_LITERAL_ADDRESS)
{
if ((sflag | F_QUERY ) & qtype)
{
flags = qtype;
if (serv->addr.sa.sa_family == AF_INET)
*addrpp = (struct all_addr *)&serv->addr.in.sin_addr;
#ifdef HAVE_IPV6
else
*addrpp = (struct all_addr *)&serv->addr.in6.sin6_addr;
#endif
}
else if (!flags)
flags = F_NOERR;
}
}
}
if (flags & ~(F_NOERR | F_NXDOMAIN)) /* flags set here means a literal found */
{
if (flags & F_QUERY)
log_query(F_CONFIG | F_FORWARD | F_NEG, qdomain, NULL, 0, NULL, 0);
else
log_query(F_CONFIG | F_FORWARD | flags, qdomain, *addrpp, 0, NULL, 0);
}
else if (qtype && (daemon->options & OPT_NODOTS_LOCAL) && !strchr(qdomain, '.'))
flags = F_NXDOMAIN;
if (flags == F_NXDOMAIN && check_for_local_domain(qdomain, now, daemon))
flags = F_NOERR;
if (flags == F_NXDOMAIN || flags == F_NOERR)
log_query(F_CONFIG | F_FORWARD | F_NEG | qtype | (flags & F_NXDOMAIN), qdomain, NULL, 0, NULL, 0);
return flags;
}
/* returns new last_server */
static void forward_query(struct daemon *daemon, int udpfd, union mysockaddr *udpaddr,
struct all_addr *dst_addr, unsigned int dst_iface,
HEADER *header, int plen, time_t now)
{
struct frec *forward;
char *domain = NULL;
int forwardall = 0, type = 0;
struct all_addr *addrp = NULL;
unsigned short flags = 0;
unsigned short gotname = extract_request(header, (unsigned int)plen, daemon->namebuff, NULL);
struct server *start = NULL;
unsigned int crc = questions_crc(header,(unsigned int)plen);
/* may be recursion not speced or no servers available. */
if (!header->rd || !daemon->servers)
forward = NULL;
else if ((forward = lookup_frec_by_sender(ntohs(header->id), udpaddr, crc)))
{
/* retry on existing query, send to all available servers */
domain = forward->sentto->domain;
if (!(daemon->options & OPT_ORDER))
{
forwardall = 1;
daemon->last_server = NULL;
}
type = forward->sentto->flags & SERV_TYPE;
if (!(start = forward->sentto->next))
start = daemon->servers; /* at end of list, recycle */
header->id = htons(forward->new_id);
}
else
{
if (gotname)
flags = search_servers(daemon, now, &addrp, gotname, daemon->namebuff, &type, &domain);
if (!flags && !(forward = get_new_frec(now)))
/* table full - server failure. */
flags = F_NEG;
if (forward)
{
/* In strict_order mode, or when using domain specific servers
always try servers in the order specified in resolv.conf,
otherwise, use the one last known to work. */
if (type != 0 || (daemon->options & OPT_ORDER))
start = daemon->servers;
else if (!(start = daemon->last_server))
{
start = daemon->servers;
forwardall = 1;
}
forward->source = *udpaddr;
forward->dest = *dst_addr;
forward->iface = dst_iface;
forward->new_id = get_id();
forward->fd = udpfd;
forward->orig_id = ntohs(header->id);
forward->crc = crc;
header->id = htons(forward->new_id);
}
}
/* check for send errors here (no route to host)
if we fail to send to all nameservers, send back an error
packet straight away (helps modem users when offline) */
if (!flags && forward)
{
struct server *firstsentto = start;
int forwarded = 0;
while (1)
{
/* only send to servers dealing with our domain.
domain may be NULL, in which case server->domain
must be NULL also. */
if (type == (start->flags & SERV_TYPE) &&
(type != SERV_HAS_DOMAIN || hostname_isequal(domain, start->domain)) &&
!(start->flags & SERV_LITERAL_ADDRESS))
{
if (sendto(start->sfd->fd, (char *)header, plen, 0,
&start->addr.sa,
sa_len(&start->addr)) == -1)
{
if (retry_send())
continue;
}
else
{
if (!gotname)
strcpy(daemon->namebuff, "query");
if (start->addr.sa.sa_family == AF_INET)
log_query(F_SERVER | F_IPV4 | F_FORWARD, daemon->namebuff,
(struct all_addr *)&start->addr.in.sin_addr, 0,
NULL, 0);
#ifdef HAVE_IPV6
else
log_query(F_SERVER | F_IPV6 | F_FORWARD, daemon->namebuff,
(struct all_addr *)&start->addr.in6.sin6_addr, 0,
NULL, 0);
#endif
forwarded = 1;
forward->sentto = start;
if (!forwardall)
break;
}
}
if (!(start = start->next))
start = daemon->servers;
if (start == firstsentto)
break;
}
if (forwarded)
return;
/* could not send on, prepare to return */
header->id = htons(forward->orig_id);
forward->new_id = 0; /* cancel */
}
/* could not send on, return empty answer or address if known for whole domain */
plen = setup_reply(header, (unsigned int)plen, addrp, flags, daemon->local_ttl);
send_from(udpfd, daemon->options & OPT_NOWILD, (char *)header, plen, udpaddr, dst_addr, dst_iface);
return;
}
static int process_reply(struct daemon *daemon, HEADER *header, time_t now,
union mysockaddr *serveraddr, unsigned int n)
{
unsigned char *pheader, *sizep;
unsigned int plen, munged = 0;
/* If upstream is advertising a larger UDP packet size
than we allow, trim it so that we don't get overlarge
requests for the client. */
if ((pheader = find_pseudoheader(header, n, &plen, &sizep)))
{
unsigned short udpsz;
unsigned char *psave = sizep;
GETSHORT(udpsz, sizep);
if (udpsz > daemon->edns_pktsz)
PUTSHORT(daemon->edns_pktsz, psave);
}
/* Complain loudly if the upstream server is non-recursive. */
if (!header->ra && header->rcode == NOERROR && ntohs(header->ancount) == 0)
{
char addrbuff[ADDRSTRLEN];
#ifdef HAVE_IPV6
if (serveraddr->sa.sa_family == AF_INET)
inet_ntop(AF_INET, &serveraddr->in.sin_addr, addrbuff, ADDRSTRLEN);
else if (serveraddr->sa.sa_family == AF_INET6)
inet_ntop(AF_INET6, &serveraddr->in6.sin6_addr, addrbuff, ADDRSTRLEN);
#else
strcpy(addrbuff, inet_ntoa(serveraddr->in.sin_addr));
#endif
syslog(LOG_WARNING, "nameserver %s refused to do a recursive query", addrbuff);
return 0;
}
if (header->opcode != QUERY || (header->rcode != NOERROR && header->rcode != NXDOMAIN))
return n;
if (daemon->bogus_addr && header->rcode != NXDOMAIN &&
check_for_bogus_wildcard(header, n, daemon->namebuff, daemon->bogus_addr, now))
{
munged = 1;
header->rcode = NXDOMAIN;
header->aa = 0;
}
else
{
if (header->rcode == NXDOMAIN &&
extract_request(header, n, daemon->namebuff, NULL) &&
check_for_local_domain(daemon->namebuff, now, daemon))
{
/* if we forwarded a query for a locally known name (because it was for
an unknown type) and the answer is NXDOMAIN, convert that to NODATA,
since we know that the domain exists, even if upstream doesn't */
munged = 1;
header->aa = 1;
header->rcode = NOERROR;
}
extract_addresses(header, n, daemon->namebuff, now, daemon);
}
/* do this after extract_addresses. Ensure NODATA reply and remove
nameserver info. */
if (munged)
{
header->ancount = htons(0);
header->nscount = htons(0);
header->arcount = htons(0);
}
/* the bogus-nxdomain stuff, doctor and NXDOMAIN->NODATA munging can all elide
sections of the packet. Find the new length here and put back pseudoheader
if it was removed. */
return resize_packet(header, n, pheader, plen);
}
/* sets new last_server */
void reply_query(struct serverfd *sfd, struct daemon *daemon, time_t now)
{
/* packet from peer server, extract data for cache, and send to
original requester */
struct frec *forward;
HEADER *header;
union mysockaddr serveraddr;
socklen_t addrlen = sizeof(serveraddr);
int n = recvfrom(sfd->fd, daemon->packet, daemon->edns_pktsz, 0, &serveraddr.sa, &addrlen);
/* Determine the address of the server replying so that we can mark that as good */
serveraddr.sa.sa_family = sfd->source_addr.sa.sa_family;
#ifdef HAVE_IPV6
if (serveraddr.sa.sa_family == AF_INET6)
serveraddr.in6.sin6_flowinfo = htonl(0);
#endif
header = (HEADER *)daemon->packet;
forward = lookup_frec(ntohs(header->id));
if (n >= (int)sizeof(HEADER) && header->qr && forward)
{
/* find good server by address if possible, otherwise assume the last one we sent to */
if ((forward->sentto->flags & SERV_TYPE) == 0)
{
struct server *last_server;
daemon->last_server = forward->sentto;
for (last_server = daemon->servers; last_server; last_server = last_server->next)
if (!(last_server->flags & (SERV_LITERAL_ADDRESS | SERV_HAS_DOMAIN | SERV_FOR_NODOTS | SERV_NO_ADDR)) &&
sockaddr_isequal(&last_server->addr, &serveraddr))
{
daemon->last_server = last_server;
break;
}
}
if ((n = process_reply(daemon, header, now, &serveraddr, (unsigned int)n)))
{
header->id = htons(forward->orig_id);
header->ra = 1; /* recursion if available */
send_from(forward->fd, daemon->options & OPT_NOWILD, daemon->packet, n,
&forward->source, &forward->dest, forward->iface);
forward->new_id = 0; /* cancel */
}
}
}
void receive_query(struct listener *listen, struct daemon *daemon, time_t now)
{
HEADER *header = (HEADER *)daemon->packet;
union mysockaddr source_addr;
unsigned short type;
struct iname *tmp;
struct all_addr dst_addr;
struct in_addr netmask, dst_addr_4;
int m, n, if_index = 0;
struct iovec iov[1];
struct msghdr msg;
struct cmsghdr *cmptr;
union {
struct cmsghdr align; /* this ensures alignment */
#ifdef HAVE_IPV6
char control6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
#endif
#if defined(IP_PKTINFO)
char control[CMSG_SPACE(sizeof(struct in_pktinfo))];
#elif defined(IP_RECVDSTADDR)
char control[CMSG_SPACE(sizeof(struct in_addr)) +
CMSG_SPACE(sizeof(struct sockaddr_dl))];
#endif
} control_u;
if (listen->family == AF_INET && (daemon->options & OPT_NOWILD))
{
dst_addr_4 = listen->iface->addr.in.sin_addr;
netmask = listen->iface->netmask;
}
else
dst_addr_4.s_addr = 0;
iov[0].iov_base = daemon->packet;
iov[0].iov_len = daemon->edns_pktsz;
msg.msg_control = control_u.control;
msg.msg_controllen = sizeof(control_u);
msg.msg_flags = 0;
msg.msg_name = &source_addr;
msg.msg_namelen = sizeof(source_addr);
msg.msg_iov = iov;
msg.msg_iovlen = 1;
if ((n = recvmsg(listen->fd, &msg, 0)) == -1)
return;
if (n < (int)sizeof(HEADER) || header->qr)
return;
source_addr.sa.sa_family = listen->family;
#ifdef HAVE_IPV6
if (listen->family == AF_INET6)
source_addr.in6.sin6_flowinfo = htonl(0);
#endif
if (!(daemon->options & OPT_NOWILD))
{
struct ifreq ifr;
if (msg.msg_controllen < sizeof(struct cmsghdr))
return;
#if defined(IP_PKTINFO)
if (listen->family == AF_INET)
for (cmptr = CMSG_FIRSTHDR(&msg); cmptr; cmptr = CMSG_NXTHDR(&msg, cmptr))
if (cmptr->cmsg_level == SOL_IP && cmptr->cmsg_type == IP_PKTINFO)
{
dst_addr_4 = dst_addr.addr.addr4 = ((struct in_pktinfo *)CMSG_DATA(cmptr))->ipi_spec_dst;
if_index = ((struct in_pktinfo *)CMSG_DATA(cmptr))->ipi_ifindex;
}
#elif defined(IP_RECVDSTADDR) && defined(IP_RECVIF)
if (listen->family == AF_INET)
{
for (cmptr = CMSG_FIRSTHDR(&msg); cmptr; cmptr = CMSG_NXTHDR(&msg, cmptr))
if (cmptr->cmsg_level == IPPROTO_IP && cmptr->cmsg_type == IP_RECVDSTADDR)
dst_addr_4 = dst_addr.addr.addr4 = *((struct in_addr *)CMSG_DATA(cmptr));
else if (cmptr->cmsg_level == IPPROTO_IP && cmptr->cmsg_type == IP_RECVIF)
if_index = ((struct sockaddr_dl *)CMSG_DATA(cmptr))->sdl_index;
}
#endif
#ifdef HAVE_IPV6
if (listen->family == AF_INET6)
{
for (cmptr = CMSG_FIRSTHDR(&msg); cmptr; cmptr = CMSG_NXTHDR(&msg, cmptr))
if (cmptr->cmsg_level == IPV6_LEVEL && cmptr->cmsg_type == IPV6_PKTINFO)
{
dst_addr.addr.addr6 = ((struct in6_pktinfo *)CMSG_DATA(cmptr))->ipi6_addr;
if_index =((struct in6_pktinfo *)CMSG_DATA(cmptr))->ipi6_ifindex;
}
}
#endif
/* enforce available interface configuration */
if (if_index == 0)
return;
if (daemon->if_except || daemon->if_names || (daemon->options & OPT_LOCALISE))
{
#ifdef SIOCGIFNAME
ifr.ifr_ifindex = if_index;
if (ioctl(listen->fd, SIOCGIFNAME, &ifr) == -1)
return;
#else
if (!if_indextoname(if_index, ifr.ifr_name))
return;
#endif
if (listen->family == AF_INET &&
(daemon->options & OPT_LOCALISE) &&
ioctl(listen->fd, SIOCGIFNETMASK, &ifr) == -1)
return;
netmask = ((struct sockaddr_in *) &ifr.ifr_addr)->sin_addr;
}
for (tmp = daemon->if_except; tmp; tmp = tmp->next)
if (tmp->name && (strcmp(tmp->name, ifr.ifr_name) == 0))
return;
if (daemon->if_names || daemon->if_addrs)
{
for (tmp = daemon->if_names; tmp; tmp = tmp->next)
if (tmp->name && (strcmp(tmp->name, ifr.ifr_name) == 0))
break;
if (!tmp)
for (tmp = daemon->if_addrs; tmp; tmp = tmp->next)
if (tmp->addr.sa.sa_family == listen->family)
{
if (tmp->addr.sa.sa_family == AF_INET &&
tmp->addr.in.sin_addr.s_addr == dst_addr.addr.addr4.s_addr)
break;
#ifdef HAVE_IPV6
else if (tmp->addr.sa.sa_family == AF_INET6 &&
memcmp(&tmp->addr.in6.sin6_addr,
&dst_addr.addr.addr6,
sizeof(struct in6_addr)) == 0)
break;
#endif
}
if (!tmp)
return;
}
}
if (extract_request(header, (unsigned int)n, daemon->namebuff, &type))
{
if (listen->family == AF_INET)
log_query(F_QUERY | F_IPV4 | F_FORWARD, daemon->namebuff,
(struct all_addr *)&source_addr.in.sin_addr, type, NULL, 0);
#ifdef HAVE_IPV6
else
log_query(F_QUERY | F_IPV6 | F_FORWARD, daemon->namebuff,
(struct all_addr *)&source_addr.in6.sin6_addr, type, NULL, 0);
#endif
}
m = answer_request (header, ((char *) header) + PACKETSZ, (unsigned int)n, daemon,
dst_addr_4, netmask, now);
if (m >= 1)
send_from(listen->fd, daemon->options & OPT_NOWILD, (char *)header, m, &source_addr, &dst_addr, if_index);
else
forward_query(daemon, listen->fd, &source_addr, &dst_addr, if_index,
header, n, now);
}
static int read_write(int fd, char *packet, int size, int rw)
{
int n, done;
for (done = 0; done < size; done += n)
{
retry:
if (rw)
n = read(fd, &packet[done], (size_t)(size - done));
else
n = write(fd, &packet[done], (size_t)(size - done));
if (n == 0)
return 0;
else if (n == -1)
{
if (retry_send())
goto retry;
else
return 0;
}
}
return 1;
}
/* The daemon forks before calling this: it should deal with one connection,
blocking as neccessary, and then return. Note, need to be a bit careful
about resources for debug mode, when the fork is suppressed: that's
done by the caller. */
char *tcp_request(struct daemon *daemon, int confd, time_t now,
struct in_addr local_addr, struct in_addr netmask)
{
int size = 0, m;
unsigned short qtype, gotname;
unsigned char c1, c2;
/* Max TCP packet + slop */
char *packet = malloc(65536 + MAXDNAME + RRFIXEDSZ);
HEADER *header;
struct server *last_server;
while (1)
{
if (!packet ||
!read_write(confd, &c1, 1, 1) || !read_write(confd, &c2, 1, 1) ||
!(size = c1 << 8 | c2) ||
!read_write(confd, packet, size, 1))
return packet;
if (size < (int)sizeof(HEADER))
continue;
header = (HEADER *)packet;
if ((gotname = extract_request(header, (unsigned int)size, daemon->namebuff, &qtype)))
{
union mysockaddr peer_addr;
socklen_t peer_len = sizeof(union mysockaddr);
if (getpeername(confd, (struct sockaddr *)&peer_addr, &peer_len) != -1)
{
if (peer_addr.sa.sa_family == AF_INET)
log_query(F_QUERY | F_IPV4 | F_FORWARD, daemon->namebuff,
(struct all_addr *)&peer_addr.in.sin_addr, qtype, NULL, 0);
#ifdef HAVE_IPV6
else
log_query(F_QUERY | F_IPV6 | F_FORWARD, daemon->namebuff,
(struct all_addr *)&peer_addr.in6.sin6_addr, qtype, NULL, 0);
#endif
}
}
/* m > 0 if answered from cache */
m = answer_request(header, ((char *) header) + 65536, (unsigned int)size, daemon,
local_addr, netmask, now);
if (m == 0)
{
unsigned short flags = 0;
struct all_addr *addrp = NULL;
int type = 0;
char *domain = NULL;
if (gotname)
flags = search_servers(daemon, now, &addrp, gotname, daemon->namebuff, &type, &domain);
if (type != 0 || (daemon->options & OPT_ORDER) || !daemon->last_server)
last_server = daemon->servers;
else
last_server = daemon->last_server;
if (!flags && last_server)
{
struct server *firstsendto = NULL;
/* Loop round available servers until we succeed in connecting to one.
Note that this code subtley ensures that consecutive queries on this connection
which can go to the same server, do so. */
while (1)
{
if (!firstsendto)
firstsendto = last_server;
else
{
if (!(last_server = last_server->next))
last_server = daemon->servers;
if (last_server == firstsendto)
break;
}
/* server for wrong domain */
if (type != (last_server->flags & SERV_TYPE) ||
(type == SERV_HAS_DOMAIN && !hostname_isequal(domain, last_server->domain)))
continue;
if ((last_server->tcpfd == -1) &&
(last_server->tcpfd = socket(last_server->addr.sa.sa_family, SOCK_STREAM, 0)) != -1 &&
connect(last_server->tcpfd, &last_server->addr.sa, sa_len(&last_server->addr)) == -1)
{
close(last_server->tcpfd);
last_server->tcpfd = -1;
}
if (last_server->tcpfd == -1)
continue;
c1 = size >> 8;
c2 = size;
if (!read_write(last_server->tcpfd, &c1, 1, 0) ||
!read_write(last_server->tcpfd, &c2, 1, 0) ||
!read_write(last_server->tcpfd, packet, size, 0) ||
!read_write(last_server->tcpfd, &c1, 1, 1) ||
!read_write(last_server->tcpfd, &c2, 1, 1))
{
close(last_server->tcpfd);
last_server->tcpfd = -1;
continue;
}
m = (c1 << 8) | c2;
if (!read_write(last_server->tcpfd, packet, m, 1))
return packet;
if (!gotname)
strcpy(daemon->namebuff, "query");
if (last_server->addr.sa.sa_family == AF_INET)
log_query(F_SERVER | F_IPV4 | F_FORWARD, daemon->namebuff,
(struct all_addr *)&last_server->addr.in.sin_addr, 0, NULL, 0);
#ifdef HAVE_IPV6
else
log_query(F_SERVER | F_IPV6 | F_FORWARD, daemon->namebuff,
(struct all_addr *)&last_server->addr.in6.sin6_addr, 0, NULL, 0);
#endif
/* There's no point in updating the cache, since this process will exit and
lose the information after one query. We make this call for the alias and
bogus-nxdomain side-effects. */
m = process_reply(daemon, header, now, &last_server->addr, (unsigned int)m);
break;
}
}
/* In case of local answer or no connections made. */
if (m == 0)
m = setup_reply(header, (unsigned int)size, addrp, flags, daemon->local_ttl);
}
c1 = m>>8;
c2 = m;
if (!read_write(confd, &c1, 1, 0) ||
!read_write(confd, &c2, 1, 0) ||
!read_write(confd, packet, m, 0))
return packet;
}
}
static struct frec *get_new_frec(time_t now)
{
struct frec *f = frec_list, *oldest = NULL;
time_t oldtime = now;
int count = 0;
static time_t warntime = 0;
while (f)
{
if (f->new_id == 0)
{
f->time = now;
return f;
}
if (difftime(f->time, oldtime) <= 0)
{
oldtime = f->time;
oldest = f;
}
count++;
f = f->next;
}
/* can't find empty one, use oldest if there is one
and it's older than timeout */
if (oldest && difftime(now, oldtime) > TIMEOUT)
{
oldest->time = now;
return oldest;
}
if (count > FTABSIZ)
{ /* limit logging rate so syslog isn't DOSed either */
if (!warntime || difftime(now, warntime) > LOGRATE)
{
warntime = now;
syslog(LOG_WARNING, "forwarding table overflow: check for server loops.");
}
return NULL;
}
if ((f = (struct frec *)malloc(sizeof(struct frec))))
{
f->next = frec_list;
f->time = now;
frec_list = f;
}
return f; /* OK if malloc fails and this is NULL */
}
static struct frec *lookup_frec(unsigned short id)
{
struct frec *f;
for(f = frec_list; f; f = f->next)
if (f->new_id == id)
return f;
return NULL;
}
static struct frec *lookup_frec_by_sender(unsigned short id,
union mysockaddr *addr,
unsigned int crc)
{
struct frec *f;
for(f = frec_list; f; f = f->next)
if (f->new_id &&
f->orig_id == id &&
f->crc == crc &&
sockaddr_isequal(&f->source, addr))
return f;
return NULL;
}
/* return unique random ids between 1 and 65535 */
static unsigned short get_id(void)
{
unsigned short ret = 0;
while (ret == 0)
{
ret = rand16();
/* scrap ids already in use */
if ((ret != 0) && lookup_frec(ret))
ret = 0;
}
return ret;
}
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