#include <sys/socket.h> /* udp(7) */
#include <netinet/in.h>
#include <netinet/udp.h>
#include <poll.h> /* poll(2) */
#include <sys/types.h> /* socket(2) */
#include <sys/socket.h>
#include <unistd.h> /* close(2) */
#include <stdio.h> /* perror(3) */
#include <sys/stat.h> /* open(2) */
#include <fcntl.h>
#include <errno.h> /* errno(3) */
#include <arpa/inet.h> /* htons(3) */
#include <netdb.h> /* getaddrinfo(3) */
#include <stdlib.h> /* atoi(3) */
#include <string.h> /* strchr(3) */
#include <time.h> /* clock_gettime(2) */
#include <signal.h> /* signal(2) */
/* #include <sys/prctl.h> */ /* prctl(2) */
/* #include <sys/wait.h> */ /* waitpid(2) */
#include <poll.h> /* poll(2) */
#include "domain2name.c"
#include "host.c"
#define HELP "find recursive DNS resolvers on IPv4 networks\n" \
"%s [-a ip] [-b ip] [-e file [-f]] [h] [-k] [-m] [-n num] [-p port] [-t μs] [-w μs] domain netwo1 [netwo2 ...]\n" \
" -a Specify the A RR IPv4 address of the domain to be used instead of getaddrinfo(3).\n" \
" -b Bind on a specific interface, defined by IPv4. Default is to use any interface.\n" \
" -e Output PCAP to filename. Any existing file is truncated. No IP/UDP checksums. See -f.\n" \
" -f Exclude sent packets from -e PCAP output They're all the same with different dst IPs.\n" \
" -h Show this help and exit.\n" \
" -k Increment IP addresses in reverse bit endianness (000 100 010 110 001 101 011 111).\n" \
" -m Spiral-search around a single host given instead of networks. Use with -n.\n" \
" -n Stops scanning after provided number of working servers is found and reported.\n" \
" -p Set the source port number to use instead of a dynamically asigned one.\n" \
" -t Number of microseconds to wait between sent packets. (default & min. 1000 - 64 KB/s)\n" \
" -w Finish after μs after last received packet when done with sending. (default 1000000)\n" \
"Network addresses are optionally followed by slash and netmask, otherwise networks are\n" \
"understood as single host addresses. Both network names and netmasks can be domains to be\n" \
"looked up or IP dot-notation addresses. Mask can also be a bit prefix (default /32).\n" \
"It would take a day to scan the entire address space (0.0.0.0/0) with the default timings.\n" \
"If network has host bits set, scanning starts at that address. 10.0.0.100/24 scans 156 hosts.\n"
/* DNS PACKET: HEADER QUESTION ANSWER AUTHORITY ADDITIONAL datatracker.ietf.org/doc/html/rfc1035
DEFINITIONS: (those appear somewhere in the packet, packet does not start with definitions!)
LABLEN 8 bits: first two bits zero, then 6 bits length of label
POINTER 16 bits: first two bits one, then 14 bits as offset from first byte of packet
STRING a single byte for defining length (0-256 - all eight bits) and then string of chars
DOMAIN i.) one or more LABLEN followed by ASCII label (no dots) end with either LABLEN 0
or a POINTER that points to some LABLEN somewhere else in the packet -OR-:
ii.) a POINTER that points to some LABLEN somewhere else in the packet
HEADER: 12 bytes
XID 16 bits: random string to be matched in response to prevent cache poisoning
/ QR 1 bit : what type is this packet? 0 quest 1 response
| OPCODE 4 bits: type of query 0 query 1 iquer 2 sstat 3-15 reserved
1 byte AA 1 bit : is response authoritative? 0 no 1 yes
| TC 1 bit : was response truncated? 0 no 1 yes
\ RD 1 bit : does query desire recursion? 0 no 1 yes
/ RA 1 bit : does response server recurse? 0 no 1 yes
1 byte Z 3 bits: reserved for future 0 only option
\ RCODE 4 bits: error condition 0 ok 1 fmter 2 srvfa 3 nxdom 4 N/I 5 forbidden
QDCOUNT 16 bits: number of questions
ANCOUNT 16 bits: number of answers
NSCOUNT 16 bits: authority section (where to ask for actual response - NS RECORDS)
ARCOUNT 16 bits: additional section (glue records)
QUESTION:
QNAME DOMAIN
QTYPE 16 bits: 1 A 2 NS 5 CNAME 6 SOA 10 NULL 12 PTR 13 HINFO 15 MX 16 TXT ...
QCLASS 16 bits: 1 INTERNET 2 CSNET (obsolete) 3 CHAOS 4 HESIOD 255 ANY ...
ANSWER:
NAME DOMAIN
TYPE same as QTYPE
CLASS same description as QCLASS, except class 255 ANY is not allowed here
TTL 32 bits: unsigned intager of seconds. for this period the record is valid.
RDLEN 16 bits: length of RDATA field - this is a number 0-65536, no two zero bits
RDATA A: 4 bytes IP address NS: DOMAIN CNAME: DOMAIN
SOA: NAME-ns1 NAME-email 32b-serial 32b-refresh 32b-retry 32b-expire 32b-nxdomainttl
NULL: any data up to RDLEN PTR: DOMAIN HINFO: STRING-CPU, STRING-OS
MX: 16 bit preference, NAME-like domain TXT: one or more STRING
*/
/* PCAP file format: GLOBALHEADER PACKETHEADER PACKETDATA PACKETHEADER2 PACKETDATA2 ...
GLOBAL HEADER: 24 bytes
MAGIC 32 bits: 0xA1B2C3D4 timestamp is s and micros 0xA1B23C4D timestamp is s and nanos
MAJOR 16 bits: version 2 https://tools.ietf.org/id/draft-gharris-opsawg-pcap-00.html
MINOR 16 bits: version 4 /-----------------------------------------------\
RESERV1 32 bits: unused and set to 0 | //en.wikipedia.org/wiki/Frame_check_sequence |
RESERV2 32 bits: unused and set to 0 \--------------------------------------------\ |
SNAPLEN 32 bits: larger or equal to size of largest capture of a single packet |
FCS 4 bits: if last bit is 1, first 3 tell nr of bytes of FCS appended to every packet
LINKTYP 28 bits: pkt type //tcpdump.org/linktypes.html 101 IPv4/v6 1 ether
PACKET HEADER: 16 bytes
SECONDS 32 bits: UNIX timestamp
SUBSECS 32 bits: nanoseconds elapsed since the second, can also be microseconds - see MAGIC
CAPTURE 32 bits: number of bytes captured from the packet following the header
ORIGLEN 32 bits: number of bytes of the original packet size (can be more than CAPTURE)
*/
/* IPv4 PACKET: HEADER DATA https://datatracker.ietf.org/doc/html/rfc791
HEADER:
/-- VERSION 4 bits: 4 IPv4 6 IPv6
| T HEADLEN 4 bits: >= 5. Header size 32 bit words (header is padded), so it points to data.
|w SRVTYPE 8 bits: 3bPrecedence 1bLowDelay 1bHighThroughput 1bHighReliability 2bReserved
|e Prec.: 0routine 1prio 2immediate 3flash 4flashoverride 5critic 110inetctrl 111netctrl
|n LENGTH 16 bits: length including header and data. every host must accept at least 576.
|t IDENTIF 16 bits: not so unique ID per src-dest persisted across fragmentations for reassembly
|y FLAGS 3 bits: bit 0 (1. bit): evil bit, bit 1: don't fragment, bit 2: more fragments
| B FOFFSET 13 bits: where in complete datagram this fragment belongs in 64 bit words-first has 0
|y TTL 8 bits: every router decreases by one, when zero, packet is destroyed
|t PROTO 8 bits: datatracker.ietf.org/doc/html/rfc790#page-6 1 ICMP 6 TCP 17 UDP
|e CHCKSUM 16 bits: 16 bit one's complement of the one's complement sum of 16b words in header
|s SRCADDR 32 bits:
\-- DSTADDR 32 bits:
OPTIONS variable: depending on type, it may be single byte-type or byte-type, byte-len, data.
Option type byte: 1b-copy to fragmented headers 2b-option class 5b-option number
Option classes: 0 control 1 reserved 2 debugging 3 reserved
Option byte zero denotes an end of options, NOOP is option number 1
PADDING variable: zero bytes ensuring header is aligned into 32 bit words
*/
/* UDP PACKET: HEADER (8 bytes) DATA https://www.ietf.org/rfc/rfc768.txt
SRCPORT 16 bits
DSTPORT 16 bits
LENGTH 16 bits: size of packet including header in bytes+8
CHCKSUM 16 bits: same algo as IP, data: pseudoheader (srcip dstip 0x0011 LENGTH) header data
*/
#define MICROSECOND 0xA1B2C3D4
#define NANOSECOND 0xA1B23C4D
#define PCAPMAJ 2
#define PCAPMIN 4
#define ETHERNET = 1,
#define IP 101
struct pcap_global {
uint32_t subsecond __attribute__((packed));
uint16_t major __attribute__((packed));
uint16_t minor __attribute__((packed));
uint32_t reserved[2] __attribute__((packed));
uint32_t snaplen __attribute__((packed));
uint32_t linktype __attribute__((packed)); /* FCS in included here for order */
} __attribute__((packed));
struct pcap_packet {
uint32_t seconds __attribute__((packed));
uint32_t subseconds __attribute__((packed));
uint32_t capture_length __attribute__((packed));
uint32_t original_length __attribute__((packed));
} __attribute__((packed));
#define LOW_DELAY (1 << 4)
#define HIGH_THROUGHPUT (1 << 3)
#define HIGH_RELIABILITY (1 << 2)
#define ROUTINE (0 << 5)
#define PRIORITY (1 << 5)
#define IMMEDIATE (1 << 6)
#define FLASH (PRIORITY | IMMEDIATE)
#define FLASH_OVERRIDE (1 << 7)
#define CRITICAL (FLASH_OVERRIDE | PRIORITY)
#define INETCTRL (FLASH_OVERRIDE | IMMEDIATE)
#define NETCTRL (FLASH_OVERRIDE | FLASH)
#define HEADLENOR (1 << 6) /* always bitwiseOR the headlen with this to apply the version number */
#define EVIL (1 << 15)
#define DF (1 << 14)
#define MF (1 << 13)
#define ICMP 1
#define TCP 6
#define UDP 17
struct ip {
uint8_t headlen; /* length of header in 32 bit words (min 5, max 15 = 60B). see HEADLENOR. */
uint8_t srvtype; /* OR here: LOW_DELAY, HIGH_THROUGHPUT, HIGH_RELIABILITY, ROUTINE, ... */
uint16_t length __attribute__((packed)); /* header + data in 8 bit words */
uint16_t identifier __attribute__((packed));
uint16_t foffset /* 64b wrds */ __attribute__((packed)); /* or any flags: EVIL, DF, MF */
uint8_t ttl; /* ignored for uint8_t */
uint8_t protocol; /* ignored for uint8_t */
uint16_t checksum; /* ignoref for uint8_t */
struct in_addr src __attribute__((packed));
struct in_addr dst __attribute__((packed)); /* ----------- 20 bytes */
char options[]; /* ignored for char[] */
} __attribute__((packed));
enum type {
A = 1,
Ns,
Md,
Cname = 5, /* we skip the quite obsolete Mf record, luckily Mf (more fragments) is also 4 */
Soa,
Mb,
Mg,
Mr,
Null,
Wks,
Ptr,
Hinfo,
Minfo,
Mx,
Txt
};
enum class {
In = 1,
Cs,
Ch,
He,
Any = 255
};
#define RESPONSE (1 << 15) /* :FLAGS */
#define QUESTION (0 << 15)
#define QUERY (0 << 11)
#define IQUERY (1 << 11)
#define STATUS (1 << 12)
#define AA (1 << 10)
#define TC (1 << 9)
#define RD (1 << 8)
#define RA (1 << 7)
#define SUCCESS (0 << 0)
#define FORMAT_ERROR (1 << 0)
#define SERVFAIL (1 << 1)
#define NXDOMAIN (FORMAT_ERROR | SERVFAIL)
#define NI (1 << 2)
#define FORBIDDEN (NXDOMAIN | FORMAT_ERROR)
struct header {
uint16_t xid __attribute__((packed));
uint16_t flags __attribute__((packed));
uint16_t qdcount __attribute__((packed));
uint16_t ancount __attribute__((packed));
uint16_t nscount __attribute__((packed));
uint16_t arcount __attribute__((packed));
char data[]; /* ignored for char[] */
} __attribute__((packed));
struct rr { /* name is omitted, first byte of struct is first byte of type */
uint16_t type __attribute__((packed));
uint16_t class __attribute__((packed));
uint32_t ttl __attribute__((packed));
uint16_t len __attribute__((packed));
char data[]; /* ignored for char[] */
} __attribute__((packed));
struct question {
uint16_t type __attribute__((packed));
uint16_t class __attribute__((packed));
} __attribute__((packed));
int logudp (int o /* fd */, struct sockaddr_in s, struct sockaddr_in d, char * u, size_t l /* d */) {
struct timespec t;
if (clock_gettime(CLOCK_REALTIME, &t) == -1) {
perror("clock_gettime(CLOCK_REALTIME, &t)");
return -2;
}
struct pcap_packet p = {
.seconds = t.tv_sec,
.subseconds = t.tv_nsec,
.capture_length = sizeof(struct ip) + l + 4*2,
.original_length = sizeof(struct ip) + l + 4*2
};
struct ip i = {
.headlen = 5 | HEADLENOR,
.srvtype = ROUTINE,
.length = htons(8+l+sizeof i),
.identifier = 0x6969,
.foffset = 0,
.ttl = 69,
.protocol = UDP,
.checksum = 0, /* wireshark does not validate, at least not on debian 11 */
.src = s.sin_addr,
.dst = d.sin_addr
};
#define LOGUDP_L (sizeof p + sizeof i + 4*2 + l)
char * c, * b = alloca(LOGUDP_L); /* to do in one write (thread safe) */
char * n = "\0"; /* as per udp rfc when no checksum was calculated (-: */
uint16_t v = htons(l+8);
c = (char *) memcpy(b, &p, sizeof p) + sizeof p;
c = (char *) memcpy(c, &i, sizeof i) + sizeof i;
c = (char *) memcpy(c, &s.sin_port, 2) + 2;
c = (char *) memcpy(c, &d.sin_port, 2) + 2;
c = (char *) memcpy(c, &v, 2) + 2;
c = (char *) memcpy(c, &n, 2) + 2;
c = (char *) memcpy(c, u, l) + l;
c++; c--; /* to make scan-build happy that c is never read */
if (write(o, b, LOGUDP_L) == -1) { /* atomic and thread safe, as per posix */
perror("write(o, b, LOGUDP_L)");
return -3;
}
return LOGUDP_L;
}
struct in_addr parse_a (const char * u, int s /* buffer size of u */, const char * d, int l, int n) {
struct in_addr r = {
.s_addr = 0 /* returns 0.0.0.0 in case of error or if no more results for n. */
};
int y = normalizedomain_len(d, l);
if (y < 0)
return r;
char * ž = alloca(y);
if (normalizedomain(ž, d, l) < 0)
return r;
const struct header * h = (const struct header *) u;
int q = ntohs(h->qdcount);
int a = ntohs(h->ancount+h->nscount+h->arcount);
char * o = NULL;
char * fuckc = NULL;
const char * c = u+sizeof(struct header);
while (q--) {
int č = name2domain_len(u, s, c);
if (č < 0)
goto r;
if (!(fuckc = realloc(o, č)))
goto r;
o = fuckc;
if (!(c = name2domain(o, u, s, c)))
goto r;
struct question * ć = (struct question *) (c+1); /* scan-build ACK: ć is not read */
ć++; ć--; /* to make scan-build happy that ć is never read */
if ((c += sizeof(*ć)+1) >= u+512)
goto r;
} /* we skip over any questions */
while (a--) {
int č = name2domain_len(u, s, c);
if (č < 0)
goto r;
if (!(fuckc = realloc(o, č)))
goto r;
o = fuckc;
if (!(c = name2domain(o, u, s, c)))
goto r;
struct rr * ć = (struct rr *) (c+1);
if (c+sizeof(*ć) >= u+512)
goto r;
if ((c += ntohs(ć->len)+sizeof(*ć)+1) >= u+512)
goto r;
if (y != č)
continue;
if (memcmp(o, ž, y))
continue;
if (ntohs(ć->type) != A)
continue;
if (ntohs(ć->class) != In)
continue;
if (ntohs(ć->len) != 4) /* this is actually a malformed packet, */
continue; /* A resource record must be four bytes */
if (n--)
continue;
r.s_addr = *(in_addr_t *) (ć->data);
goto r;
} /* we scroll over answers now and treat all three types the same, waiting for our A */
r:
free(o);
return r;
} /* returns nth IP of A record for domain d of length l in response packet u or 0.0.0.0 for err */
int finish = 0;
void handler () {
if (++finish >= 3)
exit(1);
}
int main (int argc, char ** argv) {
int r = 1;
struct in_addr a = {
.s_addr = 0
};
struct sockaddr_in b = {
.sin_family = AF_INET,
.sin_port = 0,
.sin_addr = {
.s_addr = INADDR_ANY
}
};
char * d = NULL;
int s = -1; /* socket */
int o = -1; /* output file */
struct in_net * n; /* networks */
int l; /* count of networks */
int i = 0; /* network index */
long long int j = 0; /* host in network index */
int k = 0; /* little bitendian IP address inc: 10.0.0.0, 10.128.0.0, 10.64.0.0, 10.192.0.0 */
int targetnum = 0;
int workingnum = 0;
unsigned int spiralsearch = 0;
unsigned int spiralsearch_up = 0;
unsigned int spiralsearch_down = 0;
int t = 1000;
int w = 1000000;
int e = 0; /* whether to exclude sent packets in PCAP - they're all the same */
struct in_net h; /* host to scan is .addr, h as struct in_net is returned from host() */
int notfirst = 0;
signal(SIGINT, handler);
signal(SIGTERM, handler);
while (1) {
switch (getopt(argc, argv, ":a:b:e:fhkmn:p:t:w:")) {
case 'a':
inet_aton(optarg, &a);
break;
case 'b':
inet_aton(optarg, &b.sin_addr);
break;
case 'e':
if ((o = open(optarg, O_CREAT | O_TRUNC | O_WRONLY, 00664)) == -1) {
perror("open(optarg, O_CREAT | O_TRUNC | O_WRONLY)");
r = 2;
goto r;
}
struct pcap_global g = {
.subsecond = NANOSECOND,
.major = PCAPMAJ,
.minor = PCAPMIN,
.reserved[0] = 0,
.reserved[1] = 0,
.snaplen = 65535,
.linktype = IP
};
if (write(o, &g, sizeof g) == -1) {
perror("write(o, &g, sizeof g)");
r = 3;
goto r;
}
break;
case 'f':
e++;
break;
case 'h':
printf(HELP, argv[0]);
r = 0;
goto r;
case 'k':
k++;
break;
case 'm':
spiralsearch++;
break;
case 'n':
targetnum = atoi(optarg);
break;
case 'p':
b.sin_port = htons(atoi(optarg));
break;
case 't':
t = atoi(optarg);
break;
case 'w':
w = atoi(optarg);
break;
case -1:
if (!(argc-optind)) {
fprintf(stderr, "specify domain name :: " HELP, argv[0]);
r = 4;
goto r;
}
d = argv[optind];
int e = optind+1;
if (!(l = argc-e)) {
fprintf(stderr, "specify targets to scan :: " HELP, argv[0]);
r = 5;
goto r;
}
if (spiralsearch && l != 1) {
fprintf(stderr, "-m option is set, max one host :: " HELP, argv[0]);
r = 6;
goto r;
}
n = alloca(l*sizeof *n);
for (int i = e; i < argc; i++) {
int w = i-e;
n[w] = str2net(argv[i]);
if (spiralsearch) {
n[w].mask.s_addr = INADDR_BROADCAST;
h = n[w];
}
}
goto o;
case '?':
fprintf(stderr, "unknown option :: " HELP, argv[0]);
r = 7;
goto r;
case ':':
fprintf(stderr, "missing option argument :: " HELP, argv[0]);
r = 8;
goto r;
default:
r = 9;
goto r;
}
}
o:
if (!a.s_addr) {
int e;
fprintf(stderr, "resolving %s ... ", d);
if ((e = resolve(d, &a.s_addr))) {
fprintf(stderr, "failed: %s\n", gai_strerror(e));
r = 10;
goto r;
}
fprintf(stderr, " %s\n", inet_ntoa(a));
}
if ((s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
perror("socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)");
r = 11;
goto r;
}
int ž = 1;
if (setsockopt(s, SOL_SOCKET, SO_BROADCAST, &ž, sizeof(ž)) == -1) {
perror("setsockopt(s, SOL_SOCKET, SO_BROADCAST, &ž, sizeof(ž))");
r = 12;
goto r;
} /* setting this so that sending packets to a broadcast address does not fail with noperm */
if (bind(s, (struct sockaddr *) &b, sizeof(struct sockaddr))) {
perror("bind(s, (struct sokaddr *) &b, sizeof(struct sockaddr))");
r = 13;
goto r;
}
struct timespec lp = { /* last packet */
.tv_sec = 0
};
fprintf(stderr, "starting at host number %lld\n", (j = localnumber(n[i])));
long int scanuntilhost = -1; /* no limit */
while (!finish) {
if (notfirst) {
if (k) {
if (!(j = ri(j, 32-popcnt32(n[i].mask.s_addr))))
goto k;
} else
j++;
} else
notfirst++;
if (getenv("DF_DEBUG"))
fprintf(stderr, "j = %lld, scanuntilhost = %ld\n", j, scanuntilhost);
if (spiralsearch || (h = host(n[i], j)).mask.s_addr != INADDR_BROADCAST) {
k:
if (spiralsearch) {
if (spiralsearch < 10) /* this indicates we haven't yet */
spiralsearch = 10; /* scanned given ip itself */
else {
if (spiralsearch_down == UINT32_MAX
&& spiralsearch_up == UINT32_MAX)
goto finished_sending;
if ((spiralsearch_up <= spiralsearch_down
&& spiralsearch_up != UINT32_MAX)
|| spiralsearch_down == UINT32_MAX) {
h.addr.s_addr = htonl(ntohl(n[i].addr.s_addr)
+ ++spiralsearch_up);
if (h.addr.s_addr == INADDR_BROADCAST)
spiralsearch_up = UINT32_MAX;
} else {
h.addr.s_addr = htonl(ntohl(n[i].addr.s_addr)
- ++spiralsearch_down);
if (!h.addr.s_addr)
spiralsearch_down = UINT32_MAX;
}
}
} else if (++i >= l) {
finished_sending:
fprintf(stderr, "finished sending, waiting for last replies\n");
if (clock_gettime(CLOCK_MONOTONIC, &lp) == -1) {
perror("clock_gettime(CLOCK_MONOTONIC, &z)");
r = 14;
goto r;
}
goto i;
} else {
j = localnumber(n[i]);
h = host(n[i], j);
}
}
struct sockaddr_in m = { /* I don't know much about scopes in C and I'm */
.sin_family = AF_INET, /* intentionally excercising them for the cost of */
.sin_port = htons(53), /* code unreadability. in this scope I defined h */
.sin_addr = h.addr /* as struct header, in scope above it was in_net, */
}; /* and I used h as in_net in this scope as well, */
struct header h = { /* but h as header is declared after that use (; */
.xid = 0x6969, /* oh no, cache poisoning, whatever'll I do */
.flags = htons(QUESTION | QUERY | RD),
.qdcount = htons(1),
.ancount = 0,
.nscount = 0,
.arcount = 0
};
int v = domain2name_len(d, strlen(d));
#define L (sizeof h + v + 2*2)
if (v < 0) {
r = 15;
goto r;
}
if (L > 65535) { /* pebkac, there'll be no error message here */
r = 16;
goto r;
}
char u[65535]; /* max udp packet, alloca in a loop would be bad (not scope based) */
char * c;
uint16_t y = htons(A);
uint16_t k = htons(In);
c = (char *) memcpy(u, &h, sizeof h) + sizeof h;
c += domain2name(c, d, strlen(d));
c = (char *) memcpy(c, &y, 2) + 2;
c = (char *) memcpy(c, &k, 2) + 2;
c++; c--; /* to make scan-build happy that c is never read */
int ž;
if (!e && o != -1 && (ž = logudp(o, b, m, u, L)) < -1) {
fprintf(stderr, "logudp(o, b, m, u, L) == %d\n", ž);
r = 17;
goto r;
}
if (sendto(s, u, L, 0, (struct sockaddr *) &m, sizeof(struct sockaddr_in)) == -1) {
perror("sendto(s, u, L, 0, (struct sockaddr *) &m, sizeof(struct sockad...");
r = 18;
goto r;
} /* https://stevecao.wordpress.com/2018/09/28/diagnosing-invalid-argument-error */
struct timespec z;
i:
if (clock_gettime(CLOCK_MONOTONIC, &z) == -1) {
perror("clock_gettime(CLOCK_MONOTONIC, &z)");
r = 19;
goto r;
}
if ((z.tv_sec*1000000 + z.tv_nsec/1000) - (lp.tv_sec*1000000 + lp.tv_nsec/1000) > w
&& lp.tv_sec) {
fprintf(stderr, "no more packets were received for -w μs. done.\n");
r = 0;
goto r;
}
struct pollfd q = {
.fd = s,
.events = POLLIN
};
int p;
if ((p = poll(&q, 1, t/1000 == 0 ? 1 : t/1000)) == -1) {
perror("poll(&q, 1, t/1000 == 0 ? 1 : t/1000)");
r = 20;
goto r;
}
if (!p) {
if (lp.tv_sec)
goto i;
else
continue;
}
if (q.revents & POLLERR || q.revents & POLLHUP || q.revents & POLLNVAL) {
r = 21;
goto r;
}
struct sockaddr_in f;
socklen_t č = sizeof f;
while (1) {
int š;
if ((š = recvfrom(s, u, 65535, MSG_DONTWAIT, (struct sockaddr *) &f, &č))
== -1) {
if (errno != EWOULDBLOCK) {
perror("recvfrom(s, u, 65535, MSG_DONTWAIT, (struct soc...");
r = 22;
goto r;
}
break;
}
if (lp.tv_sec)
lp = z; /* this loop ends nearly in an instant */
if (o != -1 && (ž = logudp(o, f, b, u, š)) < -1) {
fprintf(stderr, "logudp(o, f, b, u, š) == %d\n", ž);
r = 23;
goto r;
}
fprintf(stderr, "RESPONSE\t%s", inet_ntoa(f.sin_addr));
ž = 0;
struct in_addr i = parse_a(u, 65535, d, strlen(d), ž++);
while (parse_a(u, 65535, d, strlen(d), ž++).s_addr);
if (i.s_addr == a.s_addr) { /* if multithread, change printf to write. */
printf("\tWORKING");
if (ž-1 == 1 && i.s_addr)
if (++workingnum >= targetnum && targetnum) {
printf("\n");
fprintf(stderr, "discovered %d working server%s.\n",
workingnum, workingnum==1 ? "": "s");
r = 0; /* r is 1 by default */
goto r;
}
}
if (i.s_addr && i.s_addr != a.s_addr)
printf("\tLYINGWITH\t%s", inet_ntoa(i));
if (--ž > 1)
printf("\tMORETHANONE\t%d", ž);
if (!i.s_addr)
printf("\tNOA");
printf("\n");
}
if (z.tv_sec)
goto i;
}
r:
if (!r && notfirst) { /* TODO: tell EXACT packets that were sent before termination. */
char * x = alloca(l*31+strlen("SCANNED \n0")+strlen("WORKINGNUM aaaaaaaaaaaaaaaa"));
if (spiralsearch) {
strcpy(x, "SPIRALSEARCH ");
strcat(x, inet_ntoa(n[0].addr));
strcat(x, " ");
} else {
strcpy(x, "SCANNED ");
for (int m = 0; m < (finish ? i : l); m++) {
strcat(x, inet_ntoa(n[m].addr));
strcat(x, "/");
strcat(x, inet_ntoa(n[m].mask));
strcat(x, " ");
}
}
sprintf(x+strlen(x), "\nWORKINGNUM %d\n", workingnum);
write(STDIN_FILENO, x, strlen(x));
}
if (s != -1)
if (close(s))
perror("close(s)");
if (o != -1)
if (close(o))
perror("close(o)");
return r;
}
