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glibc/support/resolv_test.c

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/* DNS test framework and libresolv redirection.
Copyright (C) 2016-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <support/resolv_test.h>
#include <arpa/inet.h>
#include <errno.h>
#include <fcntl.h>
#include <nss.h>
#include <resolv.h>
#include <search.h>
#include <stdlib.h>
#include <string.h>
#include <support/check.h>
#include <support/namespace.h>
#include <support/support.h>
#include <support/test-driver.h>
#include <support/xsocket.h>
#include <support/xthread.h>
#include <support/xunistd.h>
#include <sys/uio.h>
#include <unistd.h>
/* Response builder. */
enum
{
max_response_length = 65536
};
/* Used for locating domain names containing for the purpose of
forming compression references. */
struct compressed_name
{
uint16_t offset;
unsigned char length;
unsigned char name[]; /* Without terminating NUL. */
};
static struct compressed_name *
allocate_compressed_name (const unsigned char *encoded, unsigned int offset)
{
/* Compute the length of the domain name. */
size_t length;
{
const unsigned char *p;
for (p = encoded; *p != '\0';)
{
/* No compression references are allowed. */
TEST_VERIFY (*p <= 63);
/* Skip over the label. */
p += 1 + *p;
}
length = p - encoded;
++length; /* For the terminating NUL byte. */
}
TEST_VERIFY_EXIT (length <= 255);
struct compressed_name *result
= xmalloc (offsetof (struct compressed_name, name) + length);
result->offset = offset;
result->length = length;
memcpy (result->name, encoded, length);
return result;
}
/* Convert CH to lower case. Only change letters in the ASCII
range. */
static inline unsigned char
ascii_tolower (unsigned char ch)
{
if ('A' <= ch && ch <= 'Z')
return ch - 'A' + 'a';
else
return ch;
}
/* Compare both names, for use with tsearch. The order is arbitrary,
but the comparison is case-insensitive. */
static int
compare_compressed_name (const void *left, const void *right)
{
const struct compressed_name *crleft = left;
const struct compressed_name *crright = right;
if (crleft->length != crright->length)
/* The operands are converted to int before the subtraction. */
return crleft->length - crright->length;
const unsigned char *nameleft = crleft->name;
const unsigned char *nameright = crright->name;
while (true)
{
int lenleft = *nameleft++;
int lenright = *nameright++;
/* Labels must not e compression references. */
TEST_VERIFY (lenleft <= 63);
TEST_VERIFY (lenright <= 63);
if (lenleft != lenright)
return left - right;
if (lenleft == 0)
/* End of name reached without spotting a difference. */
return 0;
/* Compare the label in a case-insensitive manner. */
const unsigned char *endnameleft = nameleft + lenleft;
while (nameleft < endnameleft)
{
int l = *nameleft++;
int r = *nameright++;
if (l != r)
{
l = ascii_tolower (l);
r = ascii_tolower (r);
if (l != r)
return l - r;
}
}
}
}
struct resolv_response_builder
{
const unsigned char *query_buffer;
size_t query_length;
size_t offset; /* Bytes written so far in buffer. */
ns_sect section; /* Current section in the DNS packet. */
unsigned int truncate_bytes; /* Bytes to remove at end of response. */
bool drop; /* Discard generated response. */
bool close; /* Close TCP client connection. */
/* Offset of the two-byte RDATA length field in the currently
written RDATA sub-structure. 0 if no RDATA is being written. */
size_t current_rdata_offset;
/* tsearch tree for locating targets for label compression. */
void *compression_offsets;
/* Must be last. Not zeroed for performance reasons. */
unsigned char buffer[max_response_length];
};
/* Response builder. */
void
resolv_response_init (struct resolv_response_builder *b,
struct resolv_response_flags flags)
{
if (b->offset > 0)
FAIL_EXIT1 ("response_init: called at offset %zu", b->offset);
if (b->query_length < 12)
FAIL_EXIT1 ("response_init called for a query of size %zu",
b->query_length);
if (flags.rcode > 15)
FAIL_EXIT1 ("response_init: invalid RCODE %u", flags.rcode);
/* Copy the transaction ID. */
b->buffer[0] = b->query_buffer[0];
b->buffer[1] = b->query_buffer[1];
/* Initialize the flags. */
b->buffer[2] = 0x80; /* Mark as response. */
b->buffer[2] |= b->query_buffer[2] & 0x01; /* Copy the RD bit. */
if (flags.tc)
b->buffer[2] |= 0x02;
b->buffer[3] = flags.rcode;
if (!flags.clear_ra)
b->buffer[3] |= 0x80;
if (flags.ad)
b->buffer[3] |= 0x20;
/* Fill in the initial section count values. */
b->buffer[4] = flags.qdcount >> 8;
b->buffer[5] = flags.qdcount;
b->buffer[6] = flags.ancount >> 8;
b->buffer[7] = flags.ancount;
b->buffer[8] = flags.nscount >> 8;
b->buffer[9] = flags.nscount;
b->buffer[10] = flags.adcount >> 8;
b->buffer[11] = flags.adcount;
b->offset = 12;
}
void
resolv_response_section (struct resolv_response_builder *b, ns_sect section)
{
if (b->offset == 0)
FAIL_EXIT1 ("resolv_response_section: response_init not called before");
if (section < b->section)
FAIL_EXIT1 ("resolv_response_section: cannot go back to previous section");
b->section = section;
}
/* Add a single byte to B. */
static inline void
response_add_byte (struct resolv_response_builder *b, unsigned char ch)
{
if (b->offset == max_response_length)
FAIL_EXIT1 ("DNS response exceeds 64 KiB limit");
b->buffer[b->offset] = ch;
++b->offset;
}
/* Add a 16-bit word VAL to B, in big-endian format. */
static void
response_add_16 (struct resolv_response_builder *b, uint16_t val)
{
response_add_byte (b, val >> 8);
response_add_byte (b, val);
}
/* Increment the pers-section record counter in the packet header. */
static void
response_count_increment (struct resolv_response_builder *b)
{
unsigned int offset = b->section;
offset = 4 + 2 * offset;
++b->buffer[offset + 1];
if (b->buffer[offset + 1] == 0)
{
/* Carry. */
++b->buffer[offset];
if (b->buffer[offset] == 0)
/* Overflow. */
FAIL_EXIT1 ("too many records in section");
}
}
void
resolv_response_add_question (struct resolv_response_builder *b,
const char *name, uint16_t class, uint16_t type)
{
if (b->offset == 0)
FAIL_EXIT1 ("resolv_response_add_question: "
"resolv_response_init not called");
if (b->section != ns_s_qd)
FAIL_EXIT1 ("resolv_response_add_question: "
"must be called in the question section");
resolv_response_add_name (b, name);
response_add_16 (b, type);
response_add_16 (b, class);
response_count_increment (b);
}
void
resolv_response_add_name (struct resolv_response_builder *b,
const char *const origname)
{
unsigned char encoded_name[NS_MAXDNAME];
if (ns_name_pton (origname, encoded_name, sizeof (encoded_name)) < 0)
FAIL_EXIT1 ("ns_name_pton (\"%s\"): %m", origname);
/* Copy the encoded name into the output buffer, apply compression
where possible. */
for (const unsigned char *name = encoded_name; ;)
{
if (*name == '\0')
{
/* We have reached the end of the name. Add the terminating
NUL byte. */
response_add_byte (b, '\0');
break;
}
/* Set to the compression target if compression is possible. */
struct compressed_name *crname_target;
/* Compression references can only reach the beginning of the
packet. */
enum { compression_limit = 1 << 12 };
{
/* The trailing part of the name to be looked up in the tree
with the compression targets. */
struct compressed_name *crname
= allocate_compressed_name (name, b->offset);
if (b->offset < compression_limit)
{
/* Add the name to the tree, for future compression
references. */
void **ptr = tsearch (crname, &b->compression_offsets,
compare_compressed_name);
if (ptr == NULL)
FAIL_EXIT1 ("tsearch out of memory");
crname_target = *ptr;
if (crname_target != crname)
/* The new name was not actually added to the tree.
Deallocate it. */
free (crname);
else
/* Signal that the tree did not yet contain the name,
but keep the allocation because it is now part of the
tree. */
crname_target = NULL;
}
else
{
/* This name cannot be reached by a compression reference.
No need to add it to the tree for future reference. */
void **ptr = tfind (crname, &b->compression_offsets,
compare_compressed_name);
if (ptr != NULL)
crname_target = *ptr;
else
crname_target = NULL;
TEST_VERIFY (crname_target != crname);
/* Not added to the tree. */
free (crname);
}
}
if (crname_target != NULL)
{
/* The name is known. Reference the previous location. */
unsigned int old_offset = crname_target->offset;
TEST_VERIFY_EXIT (old_offset < compression_limit);
response_add_byte (b, 0xC0 | (old_offset >> 8));
response_add_byte (b, old_offset);
break;
}
else
{
/* The name is new. Add this label. */
unsigned int len = 1 + *name;
resolv_response_add_data (b, name, len);
name += len;
}
}
}
void
resolv_response_open_record (struct resolv_response_builder *b,
const char *name,
uint16_t class, uint16_t type, uint32_t ttl)
{
if (b->section == ns_s_qd)
FAIL_EXIT1 ("resolv_response_open_record called in question section");
if (b->current_rdata_offset != 0)
FAIL_EXIT1 ("resolv_response_open_record called with open record");
resolv_response_add_name (b, name);
response_add_16 (b, type);
response_add_16 (b, class);
response_add_16 (b, ttl >> 16);
response_add_16 (b, ttl);
b->current_rdata_offset = b->offset;
/* Add room for the RDATA length. */
response_add_16 (b, 0);
}
void
resolv_response_close_record (struct resolv_response_builder *b)
{
size_t rdata_offset = b->current_rdata_offset;
if (rdata_offset == 0)
FAIL_EXIT1 ("response_close_record called without open record");
size_t rdata_length = b->offset - rdata_offset - 2;
if (rdata_length > 65535)
FAIL_EXIT1 ("RDATA length %zu exceeds limit", rdata_length);
b->buffer[rdata_offset] = rdata_length >> 8;
b->buffer[rdata_offset + 1] = rdata_length;
response_count_increment (b);
b->current_rdata_offset = 0;
}
void
resolv_response_add_data (struct resolv_response_builder *b,
const void *data, size_t length)
{
size_t remaining = max_response_length - b->offset;
if (remaining < length)
FAIL_EXIT1 ("resolv_response_add_data: not enough room for %zu bytes",
length);
memcpy (b->buffer + b->offset, data, length);
b->offset += length;
}
void
resolv_response_drop (struct resolv_response_builder *b)
{
b->drop = true;
}
void
resolv_response_close (struct resolv_response_builder *b)
{
b->close = true;
}
void
resolv_response_truncate_data (struct resolv_response_builder *b, size_t count)
{
if (count > 65535)
FAIL_EXIT1 ("resolv_response_truncate_data: argument too large: %zu",
count);
b->truncate_bytes = count;
}
size_t
resolv_response_length (const struct resolv_response_builder *b)
{
return b->offset;
}
unsigned char *
resolv_response_buffer (const struct resolv_response_builder *b)
{
unsigned char *result = xmalloc (b->offset);
memcpy (result, b->buffer, b->offset);
return result;
}
struct resolv_response_builder *
resolv_response_builder_allocate (const unsigned char *query_buffer,
size_t query_length)
{
struct resolv_response_builder *b = xmalloc (sizeof (*b));
memset (b, 0, offsetof (struct resolv_response_builder, buffer));
b->query_buffer = query_buffer;
b->query_length = query_length;
return b;
}
void
resolv_response_builder_free (struct resolv_response_builder *b)
{
tdestroy (b->compression_offsets, free);
free (b);
}
/* DNS query processing. */
/* Data extracted from the question section of a DNS packet. */
struct query_info
{
char qname[MAXDNAME];
uint16_t qclass;
uint16_t qtype;
struct resolv_edns_info edns;
};
/* Update *INFO from the specified DNS packet. */
static void
parse_query (struct query_info *info,
const unsigned char *buffer, size_t length)
{
HEADER hd;
_Static_assert (sizeof (hd) == 12, "DNS header size");
if (length < sizeof (hd))
FAIL_EXIT1 ("malformed DNS query: too short: %zu bytes", length);
memcpy (&hd, buffer, sizeof (hd));
if (ntohs (hd.qdcount) != 1)
FAIL_EXIT1 ("malformed DNS query: wrong question count: %d",
(int) ntohs (hd.qdcount));
if (ntohs (hd.ancount) != 0)
FAIL_EXIT1 ("malformed DNS query: wrong answer count: %d",
(int) ntohs (hd.ancount));
if (ntohs (hd.nscount) != 0)
FAIL_EXIT1 ("malformed DNS query: wrong authority count: %d",
(int) ntohs (hd.nscount));
if (ntohs (hd.arcount) > 1)
FAIL_EXIT1 ("malformed DNS query: wrong additional count: %d",
(int) ntohs (hd.arcount));
int ret = dn_expand (buffer, buffer + length, buffer + sizeof (hd),
info->qname, sizeof (info->qname));
if (ret < 0)
FAIL_EXIT1 ("malformed DNS query: cannot uncompress QNAME");
/* Obtain QTYPE and QCLASS. */
size_t remaining = length - (12 + ret);
struct
{
uint16_t qtype;
uint16_t qclass;
} qtype_qclass;
if (remaining < sizeof (qtype_qclass))
FAIL_EXIT1 ("malformed DNS query: "
"query lacks QCLASS/QTYPE, QNAME: %s", info->qname);
memcpy (&qtype_qclass, buffer + 12 + ret, sizeof (qtype_qclass));
info->qclass = ntohs (qtype_qclass.qclass);
info->qtype = ntohs (qtype_qclass.qtype);
memset (&info->edns, 0, sizeof (info->edns));
if (ntohs (hd.arcount) > 0)
{
/* Parse EDNS record. */
struct __attribute__ ((packed, aligned (1)))
{
uint8_t root;
uint16_t rtype;
uint16_t payload;
uint8_t edns_extended_rcode;
uint8_t edns_version;
uint16_t flags;
uint16_t rdatalen;
} rr;
_Static_assert (sizeof (rr) == 11, "EDNS record size");
if (remaining < 4 + sizeof (rr))
FAIL_EXIT1 ("malformed DNS query: no room for EDNS record");
memcpy (&rr, buffer + 12 + ret + 4, sizeof (rr));
if (rr.root != 0)
FAIL_EXIT1 ("malformed DNS query: invalid OPT RNAME: %d\n", rr.root);
if (rr.rtype != htons (41))
FAIL_EXIT1 ("malformed DNS query: invalid OPT type: %d\n",
ntohs (rr.rtype));
info->edns.active = true;
info->edns.extended_rcode = rr.edns_extended_rcode;
info->edns.version = rr.edns_version;
info->edns.flags = ntohs (rr.flags);
info->edns.payload_size = ntohs (rr.payload);
}
}
/* Main testing framework. */
/* Per-server information. One struct is allocated for each test
server. */
struct resolv_test_server
{
/* Local address of the server. UDP and TCP use the same port. */
struct sockaddr_in address;
/* File descriptor of the UDP server, or -1 if this server is
disabled. */
int socket_udp;
/* File descriptor of the TCP server, or -1 if this server is
disabled. */
int socket_tcp;
/* Counter of the number of responses processed so far. */
size_t response_number;
/* Thread handles for the server threads (if not disabled in the
configuration). */
pthread_t thread_udp;
pthread_t thread_tcp;
};
/* Main struct for keeping track of libresolv redirection and
testing. */
struct resolv_test
{
/* After initialization, any access to the struct must be performed
while this lock is acquired. */
pthread_mutex_t lock;
/* Data for each test server. */
struct resolv_test_server servers[resolv_max_test_servers];
/* Used if config.single_thread_udp is true. */
pthread_t thread_udp_single;
struct resolv_redirect_config config;
bool termination_requested;
};
/* Function implementing a server thread. */
typedef void (*thread_callback) (struct resolv_test *, int server_index);
/* Storage for thread-specific data, for passing to the
thread_callback function. */
struct thread_closure
{
struct resolv_test *obj; /* Current test object. */
thread_callback callback; /* Function to call. */
int server_index; /* Index of the implemented server. */
};
/* Wrap response_callback as a function which can be passed to
pthread_create. */
static void *
thread_callback_wrapper (void *arg)
{
struct thread_closure *closure = arg;
closure->callback (closure->obj, closure->server_index);
free (closure);
return NULL;
}
/* Start a server thread for the specified SERVER_INDEX, implemented
by CALLBACK. */
static pthread_t
start_server_thread (struct resolv_test *obj, int server_index,
thread_callback callback)
{
struct thread_closure *closure = xmalloc (sizeof (*closure));
*closure = (struct thread_closure)
{
.obj = obj,
.callback = callback,
.server_index = server_index,
};
return xpthread_create (NULL, thread_callback_wrapper, closure);
}
/* Process one UDP query. Return false if a termination requested has
been detected. */
static bool
server_thread_udp_process_one (struct resolv_test *obj, int server_index)
{
unsigned char query[512];
struct sockaddr_storage peer;
socklen_t peerlen = sizeof (peer);
size_t length = xrecvfrom (obj->servers[server_index].socket_udp,
query, sizeof (query), 0,
(struct sockaddr *) &peer, &peerlen);
/* Check for termination. */
{
bool termination_requested;
xpthread_mutex_lock (&obj->lock);
termination_requested = obj->termination_requested;
xpthread_mutex_unlock (&obj->lock);
if (termination_requested)
return false;
}
struct query_info qinfo;
parse_query (&qinfo, query, length);
if (test_verbose > 0)
{
if (test_verbose > 1)
printf ("info: UDP server %d: incoming query:"
" %zd bytes, %s/%u/%u, tnxid=0x%02x%02x\n",
server_index, length, qinfo.qname, qinfo.qclass, qinfo.qtype,
query[0], query[1]);
else
printf ("info: UDP server %d: incoming query:"
" %zd bytes, %s/%u/%u\n",
server_index, length, qinfo.qname, qinfo.qclass, qinfo.qtype);
}
struct resolv_response_context ctx =
{
.test = obj,
.client_address = &peer,
.client_address_length = peerlen,
.query_buffer = query,
.query_length = length,
.server_index = server_index,
.tcp = false,
.edns = qinfo.edns,
};
struct resolv_response_builder *b
= resolv_response_builder_allocate (query, length);
obj->config.response_callback
(&ctx, b, qinfo.qname, qinfo.qclass, qinfo.qtype);
if (b->drop)
{
if (test_verbose)
printf ("info: UDP server %d: dropping response to %s/%u/%u\n",
server_index, qinfo.qname, qinfo.qclass, qinfo.qtype);
}
else
{
if (test_verbose)
{
if (b->offset >= 12)
printf ("info: UDP server %d: sending response:"
" %zu bytes, RCODE %d (for %s/%u/%u)\n",
ctx.server_index, b->offset, b->buffer[3] & 0x0f,
qinfo.qname, qinfo.qclass, qinfo.qtype);
else
printf ("info: UDP server %d: sending response: %zu bytes"
" (for %s/%u/%u)\n",
server_index, b->offset,
qinfo.qname, qinfo.qclass, qinfo.qtype);
if (b->truncate_bytes > 0)
printf ("info: truncated by %u bytes\n", b->truncate_bytes);
}
resolv_response_send_udp (&ctx, b);
}
resolv_response_builder_free (b);
return true;
}
void
resolv_response_send_udp (const struct resolv_response_context *ctx,
struct resolv_response_builder *b)
{
TEST_VERIFY_EXIT (!ctx->tcp);
size_t to_send = b->offset;
if (to_send < b->truncate_bytes)
to_send = 0;
else
to_send -= b->truncate_bytes;
/* Ignore most errors here because the other end may have closed
the socket. */
if (sendto (ctx->test->servers[ctx->server_index].socket_udp,
b->buffer, to_send, 0,
ctx->client_address, ctx->client_address_length) < 0)
TEST_VERIFY_EXIT (errno != EBADF);
}
/* UDP thread_callback function. Variant for one thread per
server. */
static void
server_thread_udp (struct resolv_test *obj, int server_index)
{
while (server_thread_udp_process_one (obj, server_index))
;
}
/* Single-threaded UDP processing function, for the single_thread_udp
case. */
static void *
server_thread_udp_single (void *closure)
{
struct resolv_test *obj = closure;
struct pollfd fds[resolv_max_test_servers];
for (int server_index = 0; server_index < resolv_max_test_servers;
++server_index)
if (obj->config.servers[server_index].disable_udp)
fds[server_index] = (struct pollfd) {.fd = -1};
else
{
fds[server_index] = (struct pollfd)
{
.fd = obj->servers[server_index].socket_udp,
.events = POLLIN
};
/* Make the socket non-blocking. */
int flags = fcntl (obj->servers[server_index].socket_udp, F_GETFL, 0);
if (flags < 0)
FAIL_EXIT1 ("fcntl (F_GETFL): %m");
flags |= O_NONBLOCK;
if (fcntl (obj->servers[server_index].socket_udp, F_SETFL, flags) < 0)
FAIL_EXIT1 ("fcntl (F_SETFL): %m");
}
while (true)
{
xpoll (fds, resolv_max_test_servers, -1);
for (int server_index = 0; server_index < resolv_max_test_servers;
++server_index)
if (fds[server_index].revents != 0)
{
if (!server_thread_udp_process_one (obj, server_index))
goto out;
fds[server_index].revents = 0;
}
}
out:
return NULL;
}
/* Start the single UDP handler thread (for the single_thread_udp
case). */
static void
start_server_thread_udp_single (struct resolv_test *obj)
{
obj->thread_udp_single
= xpthread_create (NULL, server_thread_udp_single, obj);
}
/* Data describing a TCP client connect. */
struct tcp_thread_closure
{
struct resolv_test *obj;
int server_index;
int client_socket;
};
/* Read a complete DNS query packet. If EOF_OK, an immediate
end-of-file condition is acceptable. */
static bool
read_fully (int fd, void *buf, size_t len, bool eof_ok)
{
const void *const end = buf + len;
while (buf < end)
{
ssize_t ret = read (fd, buf, end - buf);
if (ret == 0)
{
if (!eof_ok)
{
support_record_failure ();
printf ("error: unexpected EOF on TCP connection\n");
}
return false;
}
else if (ret < 0)
{
if (!eof_ok || errno != ECONNRESET)
{
support_record_failure ();
printf ("error: TCP read: %m\n");
}
return false;
}
buf += ret;
eof_ok = false;
}
return true;
}
/* Write an array of iovecs. Terminate the process on failure. */
static void
writev_fully (int fd, struct iovec *buffers, size_t count)
{
while (count > 0)
{
/* Skip zero-length write requests. */
if (buffers->iov_len == 0)
{
++buffers;
--count;
continue;
}
/* Try to rewrite the remaining buffers. */
ssize_t ret = writev (fd, buffers, count);
if (ret < 0)
FAIL_EXIT1 ("writev: %m");
if (ret == 0)
FAIL_EXIT1 ("writev: invalid return value zero");
/* Find the buffers that were successfully written. */
while (ret > 0)
{
if (count == 0)
FAIL_EXIT1 ("internal writev consistency failure");
/* Current buffer was partially written. */
if (buffers->iov_len > (size_t) ret)
{
buffers->iov_base += ret;
buffers->iov_len -= ret;
ret = 0;
}
else
{
ret -= buffers->iov_len;
buffers->iov_len = 0;
++buffers;
--count;
}
}
}
}
/* Thread callback for handling a single established TCP connection to
a client. */
static void *
server_thread_tcp_client (void *arg)
{
struct tcp_thread_closure *closure = arg;
while (true)
{
/* Read packet length. */
uint16_t query_length;
if (!read_fully (closure->client_socket,
&query_length, sizeof (query_length), true))
break;
query_length = ntohs (query_length);
/* Read the packet. */
unsigned char *query_buffer = xmalloc (query_length);
read_fully (closure->client_socket, query_buffer, query_length, false);
struct query_info qinfo;
parse_query (&qinfo, query_buffer, query_length);
if (test_verbose > 0)
{
if (test_verbose > 1)
printf ("info: UDP server %d: incoming query:"
" %d bytes, %s/%u/%u, tnxid=0x%02x%02x\n",
closure->server_index, query_length,
qinfo.qname, qinfo.qclass, qinfo.qtype,
query_buffer[0], query_buffer[1]);
else
printf ("info: TCP server %d: incoming query:"
" %u bytes, %s/%u/%u\n",
closure->server_index, query_length,
qinfo.qname, qinfo.qclass, qinfo.qtype);
}
struct resolv_response_context ctx =
{
.test = closure->obj,
.query_buffer = query_buffer,
.query_length = query_length,
.server_index = closure->server_index,
.tcp = true,
.edns = qinfo.edns,
};
struct resolv_response_builder *b
= resolv_response_builder_allocate (query_buffer, query_length);
closure->obj->config.response_callback
(&ctx, b, qinfo.qname, qinfo.qclass, qinfo.qtype);
if (b->drop)
{
if (test_verbose)
printf ("info: TCP server %d: dropping response to %s/%u/%u\n",
closure->server_index,
qinfo.qname, qinfo.qclass, qinfo.qtype);
}
else
{
if (test_verbose)
printf ("info: TCP server %d: sending response: %zu bytes"
" (for %s/%u/%u)\n",
closure->server_index, b->offset,
qinfo.qname, qinfo.qclass, qinfo.qtype);
uint16_t length = htons (b->offset);
size_t to_send = b->offset;
if (to_send < b->truncate_bytes)
to_send = 0;
else
to_send -= b->truncate_bytes;
struct iovec buffers[2] =
{
{&length, sizeof (length)},
{b->buffer, to_send}
};
writev_fully (closure->client_socket, buffers, 2);
}
bool close_flag = b->close;
resolv_response_builder_free (b);
free (query_buffer);
if (close_flag)
break;
}
xclose (closure->client_socket);
free (closure);
return NULL;
}
/* thread_callback for the TCP case. Accept connections and create a
new thread for each client. */
static void
server_thread_tcp (struct resolv_test *obj, int server_index)
{
while (true)
{
/* Get the client connection. */
int client_socket = xaccept
(obj->servers[server_index].socket_tcp, NULL, NULL);
/* Check for termination. */
xpthread_mutex_lock (&obj->lock);
if (obj->termination_requested)
{
xpthread_mutex_unlock (&obj->lock);
xclose (client_socket);
break;
}
xpthread_mutex_unlock (&obj->lock);
/* Spawn a new thread for handling this connection. */
struct tcp_thread_closure *closure = xmalloc (sizeof (*closure));
*closure = (struct tcp_thread_closure)
{
.obj = obj,
.server_index = server_index,
.client_socket = client_socket,
};
pthread_t thr
= xpthread_create (NULL, server_thread_tcp_client, closure);
/* TODO: We should keep track of this thread so that we can
block in resolv_test_end until it has exited. */
xpthread_detach (thr);
}
}
/* Create UDP and TCP server sockets. */
static void
make_server_sockets (struct resolv_test_server *server)
{
while (true)
{
server->socket_udp = xsocket (AF_INET, SOCK_DGRAM, IPPROTO_UDP);
server->socket_tcp = xsocket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
/* Pick the address for the UDP socket. */
server->address = (struct sockaddr_in)
{
.sin_family = AF_INET,
.sin_addr = {.s_addr = htonl (INADDR_LOOPBACK)}
};
xbind (server->socket_udp,
(struct sockaddr *)&server->address, sizeof (server->address));
/* Retrieve the address. */
socklen_t addrlen = sizeof (server->address);
xgetsockname (server->socket_udp,
(struct sockaddr *)&server->address, &addrlen);
/* Bind the TCP socket to the same address. */
{
int on = 1;
xsetsockopt (server->socket_tcp, SOL_SOCKET, SO_REUSEADDR,
&on, sizeof (on));
}
if (bind (server->socket_tcp,
(struct sockaddr *)&server->address,
sizeof (server->address)) != 0)
{
/* Port collision. The UDP bind succeeded, but the TCP BIND
failed. We assume here that the kernel will pick the
next local UDP address randomly. */
if (errno == EADDRINUSE)
{
xclose (server->socket_udp);
xclose (server->socket_tcp);
continue;
}
FAIL_EXIT1 ("TCP bind: %m");
}
xlisten (server->socket_tcp, 5);
break;
}
}
/* Like make_server_sockets, but the caller supplies the address to
use. */
static void
make_server_sockets_for_address (struct resolv_test_server *server,
const struct sockaddr *addr)
{
server->socket_udp = xsocket (AF_INET, SOCK_DGRAM, IPPROTO_UDP);
server->socket_tcp = xsocket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (addr->sa_family == AF_INET)
server->address = *(const struct sockaddr_in *) addr;
else
/* We cannot store the server address in the socket. This should
not matter if disable_redirect is used. */
server->address = (struct sockaddr_in) { .sin_family = 0, };
xbind (server->socket_udp,
(struct sockaddr *)&server->address, sizeof (server->address));
xbind (server->socket_tcp,
(struct sockaddr *)&server->address, sizeof (server->address));
xlisten (server->socket_tcp, 5);
}
/* One-time initialization of NSS. */
static void
resolv_redirect_once (void)
{
/* Only use nss_dns. */
__nss_configure_lookup ("hosts", "dns");
__nss_configure_lookup ("networks", "dns");
/* Enter a network namespace for isolation and firewall state
cleanup. The tests will still work if these steps fail, but they
may be less reliable. */
support_become_root ();
support_enter_network_namespace ();
}
pthread_once_t resolv_redirect_once_var = PTHREAD_ONCE_INIT;
void
resolv_test_init (void)
{
/* Perform one-time initialization of NSS. */
xpthread_once (&resolv_redirect_once_var, resolv_redirect_once);
}
/* Copy the search path from CONFIG.search to the _res object. */
static void
set_search_path (struct resolv_redirect_config config)
{
memset (_res.defdname, 0, sizeof (_res.defdname));
memset (_res.dnsrch, 0, sizeof (_res.dnsrch));
char *current = _res.defdname;
char *end = current + sizeof (_res.defdname);
for (unsigned int i = 0;
i < sizeof (config.search) / sizeof (config.search[0]); ++i)
{
if (config.search[i] == NULL)
continue;
size_t length = strlen (config.search[i]) + 1;
size_t remaining = end - current;
TEST_VERIFY_EXIT (length <= remaining);
memcpy (current, config.search[i], length);
_res.dnsrch[i] = current;
current += length;
}
}
struct resolv_test *
resolv_test_start (struct resolv_redirect_config config)
{
/* Apply configuration defaults. */
if (config.nscount == 0)
config.nscount = resolv_max_test_servers;
struct resolv_test *obj = xmalloc (sizeof (*obj));
*obj = (struct resolv_test) {
.config = config,
.lock = PTHREAD_MUTEX_INITIALIZER,
};
if (!config.disable_redirect)
resolv_test_init ();
/* Create all the servers, to reserve the necessary ports. */
for (int server_index = 0; server_index < config.nscount; ++server_index)
if (config.disable_redirect && config.server_address_overrides != NULL)
make_server_sockets_for_address
(obj->servers + server_index,
config.server_address_overrides[server_index]);
else
make_server_sockets (obj->servers + server_index);
/* Start server threads. Disable the server ports, as
requested. */
for (int server_index = 0; server_index < config.nscount; ++server_index)
{
struct resolv_test_server *server = obj->servers + server_index;
if (config.servers[server_index].disable_udp)
{
xclose (server->socket_udp);
server->socket_udp = -1;
}
else if (!config.single_thread_udp)
server->thread_udp = start_server_thread (obj, server_index,
server_thread_udp);
if (config.servers[server_index].disable_tcp)
{
xclose (server->socket_tcp);
server->socket_tcp = -1;
}
else
server->thread_tcp = start_server_thread (obj, server_index,
server_thread_tcp);
}
if (config.single_thread_udp)
start_server_thread_udp_single (obj);
if (config.disable_redirect)
return obj;
int timeout = 1;
/* Initialize libresolv. */
TEST_VERIFY_EXIT (res_init () == 0);
/* Disable IPv6 name server addresses. The code below only
overrides the IPv4 addresses. */
__res_iclose (&_res, true);
_res._u._ext.nscount = 0;
/* Redirect queries to the server socket. */
if (test_verbose)
{
printf ("info: old timeout value: %d\n", _res.retrans);
printf ("info: old retry attempt value: %d\n", _res.retry);
printf ("info: old _res.options: 0x%lx\n", _res.options);
printf ("info: old _res.nscount value: %d\n", _res.nscount);
printf ("info: old _res.ndots value: %d\n", _res.ndots);
}
_res.retrans = timeout;
_res.retry = 4;
_res.nscount = config.nscount;
_res.options = RES_INIT | RES_RECURSE | RES_DEFNAMES | RES_DNSRCH;
_res.ndots = 1;
if (test_verbose)
{
printf ("info: new timeout value: %d\n", _res.retrans);
printf ("info: new retry attempt value: %d\n", _res.retry);
printf ("info: new _res.options: 0x%lx\n", _res.options);
printf ("info: new _res.nscount value: %d\n", _res.nscount);
printf ("info: new _res.ndots value: %d\n", _res.ndots);
}
for (int server_index = 0; server_index < config.nscount; ++server_index)
{
TEST_VERIFY_EXIT (obj->servers[server_index].address.sin_port != 0);
_res.nsaddr_list[server_index] = obj->servers[server_index].address;
if (test_verbose)
{
char buf[256];
TEST_VERIFY_EXIT
(inet_ntop (AF_INET, &obj->servers[server_index].address.sin_addr,
buf, sizeof (buf)) != NULL);
printf ("info: server %d: %s/%u\n",
server_index, buf,
htons (obj->servers[server_index].address.sin_port));
}
}
set_search_path (config);
return obj;
}
void
resolv_test_end (struct resolv_test *obj)
{
res_close ();
xpthread_mutex_lock (&obj->lock);
obj->termination_requested = true;
xpthread_mutex_unlock (&obj->lock);
/* Send trigger packets to unblock the server threads. */
for (int server_index = 0; server_index < obj->config.nscount;
++server_index)
{
if (!obj->config.servers[server_index].disable_udp)
{
int sock = xsocket (AF_INET, SOCK_DGRAM, IPPROTO_UDP);
xsendto (sock, "", 1, 0,
(struct sockaddr *) &obj->servers[server_index].address,
sizeof (obj->servers[server_index].address));
xclose (sock);
}
if (!obj->config.servers[server_index].disable_tcp)
{
int sock = xsocket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
xconnect (sock,
(struct sockaddr *) &obj->servers[server_index].address,
sizeof (obj->servers[server_index].address));
xclose (sock);
}
}
if (obj->config.single_thread_udp)
xpthread_join (obj->thread_udp_single);
/* Wait for the server threads to terminate. */
for (int server_index = 0; server_index < obj->config.nscount;
++server_index)
{
if (!obj->config.servers[server_index].disable_udp)
{
if (!obj->config.single_thread_udp)
xpthread_join (obj->servers[server_index].thread_udp);
xclose (obj->servers[server_index].socket_udp);
}
if (!obj->config.servers[server_index].disable_tcp)
{
xpthread_join (obj->servers[server_index].thread_tcp);
xclose (obj->servers[server_index].socket_tcp);
}
}
free (obj);
}
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