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Impove cache behaviour for TCP connections.

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For ease of implementaion, dnsmasq has always forked a new process to
handle each incoming TCP connection. A side-effect of this is that any
DNS queries answered from TCP connections are not cached: when TCP
connections were rare, this was not a problem.  With the coming of
DNSSEC, it's now the case that some DNSSEC queries have answers which
spill to TCP, and if, for instance, this applies to the keys for the
root then those never get cached, and performance is very bad.  This
fix passes cache entries back from the TCP child process to the main
server process, and fixes the problem.
This commit is contained in:
Simon Kelley
2018-10-18 19:35:29 +01:00
parent 91421cb757
commit a799ca0c63
5 changed files with 291 additions and 19 deletions
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37
src/blockdata.c
View File

@@ -61,7 +61,7 @@ void blockdata_report(void)
blockdata_alloced * sizeof(struct blockdata));
}
struct blockdata *blockdata_alloc(char *data, size_t len)
static struct blockdata *blockdata_alloc_real(int fd, char *data, size_t len)
{
struct blockdata *block, *ret = NULL;
struct blockdata **prev = &ret;
@@ -89,8 +89,17 @@ struct blockdata *blockdata_alloc(char *data, size_t len)
blockdata_hwm = blockdata_count;
blen = len > KEYBLOCK_LEN ? KEYBLOCK_LEN : len;
memcpy(block->key, data, blen);
data += blen;
if (data)
{
memcpy(block->key, data, blen);
data += blen;
}
else if (!read_write(fd, block->key, blen, 1))
{
/* failed read free partial chain */
blockdata_free(ret);
return NULL;
}
len -= blen;
*prev = block;
prev = &block->next;
@@ -100,6 +109,10 @@ struct blockdata *blockdata_alloc(char *data, size_t len)
return ret;
}
struct blockdata *blockdata_alloc(char *data, size_t len)
{
return blockdata_alloc_real(0, data, len);
}
void blockdata_free(struct blockdata *blocks)
{
@@ -148,5 +161,21 @@ void *blockdata_retrieve(struct blockdata *block, size_t len, void *data)
return data;
}
void blockdata_write(struct blockdata *block, size_t len, int fd)
{
for (; len > 0 && block; block = block->next)
{
size_t blen = len > KEYBLOCK_LEN ? KEYBLOCK_LEN : len;
read_write(fd, block->key, blen, 0);
len -= blen;
}
}
struct blockdata *blockdata_read(int fd, size_t len)
{
return blockdata_alloc_real(fd, NULL, len);
}
#endif

196
src/cache.c
View File

@@ -26,6 +26,8 @@ static union bigname *big_free = NULL;
static int bignames_left, hash_size;
static void make_non_terminals(struct crec *source);
static struct crec *really_insert(char *name, struct all_addr *addr,
time_t now, unsigned long ttl, unsigned short flags);
/* type->string mapping: this is also used by the name-hash function as a mixing table. */
static const struct {
@@ -464,16 +466,10 @@ void cache_start_insert(void)
new_chain = NULL;
insert_error = 0;
}
struct crec *cache_insert(char *name, struct all_addr *addr,
time_t now, unsigned long ttl, unsigned short flags)
{
struct crec *new, *target_crec = NULL;
union bigname *big_name = NULL;
int freed_all = flags & F_REVERSE;
int free_avail = 0;
unsigned int target_uid;
/* Don't log DNSSEC records here, done elsewhere */
if (flags & (F_IPV4 | F_IPV6 | F_CNAME))
{
@@ -484,7 +480,20 @@ struct crec *cache_insert(char *name, struct all_addr *addr,
if (daemon->min_cache_ttl != 0 && daemon->min_cache_ttl > ttl)
ttl = daemon->min_cache_ttl;
}
return really_insert(name, addr, now, ttl, flags);
}
static struct crec *really_insert(char *name, struct all_addr *addr,
time_t now, unsigned long ttl, unsigned short flags)
{
struct crec *new, *target_crec = NULL;
union bigname *big_name = NULL;
int freed_all = flags & F_REVERSE;
int free_avail = 0;
unsigned int target_uid;
/* if previous insertion failed give up now. */
if (insert_error)
return NULL;
@@ -645,12 +654,185 @@ void cache_end_insert(void)
cache_hash(new_chain);
cache_link(new_chain);
daemon->metrics[METRIC_DNS_CACHE_INSERTED]++;
/* If we're a child process, send this cache entry up the pipe to the master.
The marshalling process is rather nasty. */
if (daemon->pipe_to_parent != -1)
{
char *name = cache_get_name(new_chain);
ssize_t m = strlen(name);
unsigned short flags = new_chain->flags;
#ifdef HAVE_DNSSEC
u16 class = new_chain->uid;
#endif
read_write(daemon->pipe_to_parent, (unsigned char *)&m, sizeof(m), 0);
read_write(daemon->pipe_to_parent, (unsigned char *)name, m, 0);
read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->ttd, sizeof(new_chain->ttd), 0);
read_write(daemon->pipe_to_parent, (unsigned char *)&flags, sizeof(flags), 0);
if (flags & (F_IPV4 | F_IPV6))
read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr, sizeof(new_chain->addr), 0);
#ifdef HAVE_DNSSEC
else if (flags & F_DNSKEY)
{
read_write(daemon->pipe_to_parent, (unsigned char *)&class, sizeof(class), 0);
read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.key.algo, sizeof(new_chain->addr.key.algo), 0);
read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.key.keytag, sizeof(new_chain->addr.key.keytag), 0);
read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.key.flags, sizeof(new_chain->addr.key.flags), 0);
read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.key.keylen, sizeof(new_chain->addr.key.keylen), 0);
blockdata_write(new_chain->addr.key.keydata, new_chain->addr.key.keylen, daemon->pipe_to_parent);
}
else if (flags & F_DS)
{
read_write(daemon->pipe_to_parent, (unsigned char *)&class, sizeof(class), 0);
/* A negative DS entry is possible and has no data, obviously. */
if (!(flags & F_NEG))
{
read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.ds.algo, sizeof(new_chain->addr.ds.algo), 0);
read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.ds.keytag, sizeof(new_chain->addr.ds.keytag), 0);
read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.ds.digest, sizeof(new_chain->addr.ds.digest), 0);
read_write(daemon->pipe_to_parent, (unsigned char *)&new_chain->addr.ds.keylen, sizeof(new_chain->addr.ds.keylen), 0);
blockdata_write(new_chain->addr.ds.keydata, new_chain->addr.ds.keylen, daemon->pipe_to_parent);
}
}
#endif
}
}
new_chain = tmp;
}
/* signal end of cache insert in master process */
if (daemon->pipe_to_parent != -1)
{
ssize_t m = -1;
read_write(daemon->pipe_to_parent, (unsigned char *)&m, sizeof(m), 0);
}
new_chain = NULL;
}
/* A marshalled cache entry arrives on fd, read, unmarshall and insert into cache of master process. */
int cache_recv_insert(time_t now, int fd)
{
ssize_t m;
struct all_addr addr;
unsigned long ttl;
time_t ttd;
unsigned short flags;
struct crec *crecp = NULL;
cache_start_insert();
while(1)
{
if (!read_write(fd, (unsigned char *)&m, sizeof(m), 1))
return 0;
if (m == -1)
{
cache_end_insert();
return 1;
}
if (!read_write(fd, (unsigned char *)daemon->namebuff, m, 1) ||
!read_write(fd, (unsigned char *)&ttd, sizeof(ttd), 1) ||
!read_write(fd, (unsigned char *)&flags, sizeof(flags), 1))
return 0;
daemon->namebuff[m] = 0;
ttl = difftime(ttd, now);
if (flags & (F_IPV4 | F_IPV6))
{
if (!read_write(fd, (unsigned char *)&addr, sizeof(addr), 1))
return 0;
crecp = really_insert(daemon->namebuff, &addr, now, ttl, flags);
}
else if (flags & F_CNAME)
{
struct crec *newc = really_insert(daemon->namebuff, NULL, now, ttl, flags);
/* This relies on the fact the the target of a CNAME immediately preceeds
it because of the order of extraction in extract_addresses, and
the order reversal on the new_chain. */
if (newc)
{
if (!crecp)
{
newc->addr.cname.target.cache = NULL;
/* anything other than zero, to avoid being mistaken for CNAME to interface-name */
newc->addr.cname.uid = 1;
}
else
{
next_uid(crecp);
newc->addr.cname.target.cache = crecp;
newc->addr.cname.uid = crecp->uid;
}
}
}
#ifdef HAVE_DNSSEC
else if (flags & (F_DNSKEY | F_DS))
{
unsigned short class, keylen, keyflags, keytag;
unsigned char algo, digest;
struct blockdata *keydata;
if (!read_write(fd, (unsigned char *)&class, sizeof(class), 1))
return 0;
/* Cache needs to known class for DNSSEC stuff */
addr.addr.dnssec.class = class;
crecp = really_insert(daemon->namebuff, &addr, now, ttl, flags);
if (flags & F_DNSKEY)
{
if (!read_write(fd, (unsigned char *)&algo, sizeof(algo), 1) ||
!read_write(fd, (unsigned char *)&keytag, sizeof(keytag), 1) ||
!read_write(fd, (unsigned char *)&keyflags, sizeof(keyflags), 1) ||
!read_write(fd, (unsigned char *)&keylen, sizeof(keylen), 1) ||
!(keydata = blockdata_read(fd, keylen)))
return 0;
}
else if (!(flags & F_NEG))
{
if (!read_write(fd, (unsigned char *)&algo, sizeof(algo), 1) ||
!read_write(fd, (unsigned char *)&keytag, sizeof(keytag), 1) ||
!read_write(fd, (unsigned char *)&digest, sizeof(digest), 1) ||
!read_write(fd, (unsigned char *)&keylen, sizeof(keylen), 1) ||
!(keydata = blockdata_read(fd, keylen)))
return 0;
}
if (crecp)
{
if (flags & F_DNSKEY)
{
crecp->addr.key.algo = algo;
crecp->addr.key.keytag = keytag;
crecp->addr.key.flags = flags;
crecp->addr.key.keylen = keylen;
crecp->addr.key.keydata = keydata;
}
else if (!(flags & F_NEG))
{
crecp->addr.ds.algo = algo;
crecp->addr.ds.keytag = keytag;
crecp->addr.ds.digest = digest;
crecp->addr.ds.keylen = keylen;
crecp->addr.ds.keydata = keydata;
}
}
}
#endif
}
}
int cache_find_non_terminal(char *name, time_t now)
{
struct crec *crecp;

58
src/dnsmasq.c
View File

@@ -930,6 +930,10 @@ int main (int argc, char **argv)
check_servers();
pid = getpid();
daemon->pipe_to_parent = -1;
for (i = 0; i < MAX_PROCS; i++)
daemon->tcp_pipes[i] = -1;
#ifdef HAVE_INOTIFY
/* Using inotify, have to select a resolv file at startup */
@@ -1611,7 +1615,7 @@ static int set_dns_listeners(time_t now)
we don't need to explicitly arrange to wake up here */
if (listener->tcpfd != -1)
for (i = 0; i < MAX_PROCS; i++)
if (daemon->tcp_pids[i] == 0)
if (daemon->tcp_pids[i] == 0 && daemon->tcp_pipes[i] == -1)
{
poll_listen(listener->tcpfd, POLLIN);
break;
@@ -1624,6 +1628,13 @@ static int set_dns_listeners(time_t now)
}
#ifndef NO_FORK
if (!option_bool(OPT_DEBUG))
for (i = 0; i < MAX_PROCS; i++)
if (daemon->tcp_pipes[i] != -1)
poll_listen(daemon->tcp_pipes[i], POLLIN);
#endif
return wait;
}
@@ -1632,7 +1643,10 @@ static void check_dns_listeners(time_t now)
struct serverfd *serverfdp;
struct listener *listener;
int i;
#ifndef NO_FORK
int pipefd[2];
#endif
for (serverfdp = daemon->sfds; serverfdp; serverfdp = serverfdp->next)
if (poll_check(serverfdp->fd, POLLIN))
reply_query(serverfdp->fd, serverfdp->source_addr.sa.sa_family, now);
@@ -1642,7 +1656,26 @@ static void check_dns_listeners(time_t now)
if (daemon->randomsocks[i].refcount != 0 &&
poll_check(daemon->randomsocks[i].fd, POLLIN))
reply_query(daemon->randomsocks[i].fd, daemon->randomsocks[i].family, now);
#ifndef NO_FORK
/* Races. The child process can die before we read all of the data from the
pipe, or vice versa. Therefore send tcp_pids to zero when we wait() the
process, and tcp_pipes to -1 and close the FD when we read the last
of the data - indicated by cache_recv_insert returning zero.
The order of these events is indeterminate, and both are needed
to free the process slot. Once the child process has gone, poll()
returns POLLHUP, not POLLIN, so have to check for both here. */
if (!option_bool(OPT_DEBUG))
for (i = 0; i < MAX_PROCS; i++)
if (daemon->tcp_pipes[i] != -1 &&
poll_check(daemon->tcp_pipes[i], POLLIN | POLLHUP) &&
!cache_recv_insert(now, daemon->tcp_pipes[i]))
{
close(daemon->tcp_pipes[i]);
daemon->tcp_pipes[i] = -1;
}
#endif
for (listener = daemon->listeners; listener; listener = listener->next)
{
if (listener->fd != -1 && poll_check(listener->fd, POLLIN))
@@ -1736,15 +1769,20 @@ static void check_dns_listeners(time_t now)
while (retry_send(close(confd)));
}
#ifndef NO_FORK
else if (!option_bool(OPT_DEBUG) && (p = fork()) != 0)
else if (!option_bool(OPT_DEBUG) && pipe(pipefd) == 0 && (p = fork()) != 0)
{
if (p != -1)
close(pipefd[1]); /* parent needs read pipe end. */
if (p == -1)
close(pipefd[0]);
else
{
int i;
for (i = 0; i < MAX_PROCS; i++)
if (daemon->tcp_pids[i] == 0)
if (daemon->tcp_pids[i] == 0 && daemon->tcp_pipes[i] == -1)
{
daemon->tcp_pids[i] = p;
daemon->tcp_pipes[i] = pipefd[0];
break;
}
}
@@ -1761,7 +1799,7 @@ static void check_dns_listeners(time_t now)
int flags;
struct in_addr netmask;
int auth_dns;
if (iface)
{
netmask = iface->netmask;
@@ -1777,7 +1815,11 @@ static void check_dns_listeners(time_t now)
/* Arrange for SIGALRM after CHILD_LIFETIME seconds to
terminate the process. */
if (!option_bool(OPT_DEBUG))
alarm(CHILD_LIFETIME);
{
alarm(CHILD_LIFETIME);
close(pipefd[0]); /* close read end in child. */
daemon->pipe_to_parent = pipefd[1];
}
#endif
/* start with no upstream connections. */

5
src/dnsmasq.h
View File

@@ -1091,6 +1091,8 @@ extern struct daemon {
size_t packet_len; /* " " */
struct randfd *rfd_save; /* " " */
pid_t tcp_pids[MAX_PROCS];
int tcp_pipes[MAX_PROCS];
int pipe_to_parent;
struct randfd randomsocks[RANDOM_SOCKS];
int v6pktinfo;
struct addrlist *interface_addrs; /* list of all addresses/prefix lengths associated with all local interfaces */
@@ -1152,6 +1154,7 @@ struct crec *cache_find_by_name(struct crec *crecp,
char *name, time_t now, unsigned int prot);
void cache_end_insert(void);
void cache_start_insert(void);
int cache_recv_insert(time_t now, int fd);
struct crec *cache_insert(char *name, struct all_addr *addr,
time_t now, unsigned long ttl, unsigned short flags);
void cache_reload(void);
@@ -1174,6 +1177,8 @@ void blockdata_init(void);
void blockdata_report(void);
struct blockdata *blockdata_alloc(char *data, size_t len);
void *blockdata_retrieve(struct blockdata *block, size_t len, void *data);
struct blockdata *blockdata_read(int fd, size_t len);
void blockdata_write(struct blockdata *block, size_t len, int fd);
void blockdata_free(struct blockdata *blocks);
#endif