| [c5c522c] | 1 | From: Aron Xu <aron@debian.org> |
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| 2 | Date: Mon, 13 Feb 2012 19:06:52 +0800 |
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| 3 | Subject: misc connection failures |
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| 4 | |
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| 5 | --- |
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| 6 | nc.1 | 76 ++++++++++++++++++++++++++++++++++++--- |
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| 7 | netcat.c | 119 ++++++++++++++++++++++++++++++++++++++++++-------------------- |
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| 8 | 2 files changed, 153 insertions(+), 42 deletions(-) |
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| 9 | |
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| 10 | diff --git a/nc.1 b/nc.1 |
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| 11 | index 60e3668..477cb1b 100644 |
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| 12 | --- a/nc.1 |
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| 13 | +++ b/nc.1 |
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| 14 | @@ -34,7 +34,7 @@ |
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| 15 | .Sh SYNOPSIS |
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| 16 | .Nm nc |
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| 17 | .Bk -words |
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| 18 | -.Op Fl 46CDdhklnrStUuvZz |
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| 19 | +.Op Fl 46bCDdhklnrStUuvZz |
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| 20 | .Op Fl I Ar length |
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| 21 | .Op Fl i Ar interval |
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| 22 | .Op Fl O Ar length |
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| 23 | @@ -99,6 +99,8 @@ to use IPv4 addresses only. |
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| 24 | Forces |
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| 25 | .Nm |
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| 26 | to use IPv6 addresses only. |
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| 27 | +.It Fl b |
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| 28 | +Allow broadcast. |
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| 29 | .It Fl C |
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| 30 | Send CRLF as line-ending. |
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| 31 | .It Fl D |
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| 32 | @@ -323,6 +325,54 @@ and which side is being used as a |
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| 33 | The connection may be terminated using an |
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| 34 | .Dv EOF |
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| 35 | .Pq Sq ^D . |
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| 36 | +.Pp |
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| 37 | +There is no |
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| 38 | +.Fl c |
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| 39 | +or |
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| 40 | +.Fl e |
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| 41 | +option in this netcat, but you still can execute a command after connection |
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| 42 | +being established by redirecting file descriptors. Be cautious here because |
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| 43 | +opening a port and let anyone connected execute arbitrary command on your |
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| 44 | +site is DANGEROUS. If you really need to do this, here is an example: |
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| 45 | +.Pp |
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| 46 | +On |
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| 47 | +.Sq server |
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| 48 | +side: |
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| 49 | +.Pp |
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| 50 | +.Dl $ rm -f /tmp/f; mkfifo /tmp/f |
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| 51 | +.Dl $ cat /tmp/f | /bin/sh -i 2>&1 | nc -l 127.0.0.1 1234 > /tmp/f |
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| 52 | +.Pp |
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| 53 | +On |
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| 54 | +.Sq client |
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| 55 | +side: |
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| 56 | +.Pp |
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| 57 | +.Dl $ nc host.example.com 1234 |
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| 58 | +.Dl $ (shell prompt from host.example.com) |
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| 59 | +.Pp |
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| 60 | +By doing this, you create a fifo at /tmp/f and make nc listen at port 1234 |
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| 61 | +of address 127.0.0.1 on |
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| 62 | +.Sq server |
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| 63 | +side, when a |
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| 64 | +.Sq client |
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| 65 | +establishes a connection successfully to that port, /bin/sh gets executed |
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| 66 | +on |
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| 67 | +.Sq server |
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| 68 | +side and the shell prompt is given to |
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| 69 | +.Sq client |
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| 70 | +side. |
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| 71 | +.Pp |
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| 72 | +When connection is terminated, |
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| 73 | +.Nm |
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| 74 | +quits as well. Use |
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| 75 | +.Fl k |
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| 76 | +if you want it keep listening, but if the command quits this option won't |
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| 77 | +restart it or keep |
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| 78 | +.Nm |
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| 79 | +running. Also don't forget to remove the file descriptor once you don't need |
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| 80 | +it anymore: |
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| 81 | +.Pp |
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| 82 | +.Dl $ rm -f /tmp/f |
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| 83 | +.Pp |
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| 84 | .Sh DATA TRANSFER |
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| 85 | The example in the previous section can be expanded to build a |
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| 86 | basic data transfer model. |
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| 87 | @@ -382,15 +432,30 @@ The |
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| 88 | flag can be used to tell |
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| 89 | .Nm |
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| 90 | to report open ports, |
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| 91 | -rather than initiate a connection. |
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| 92 | +rather than initiate a connection. Usually it's useful to turn on verbose |
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| 93 | +output to stderr by use this option in conjunction with |
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| 94 | +.Fl v |
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| 95 | +option. |
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| 96 | +.Pp |
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| 97 | For example: |
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| 98 | .Bd -literal -offset indent |
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| 99 | -$ nc -z host.example.com 20-30 |
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| 100 | +$ nc \-zv host.example.com 20-30 |
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| 101 | Connection to host.example.com 22 port [tcp/ssh] succeeded! |
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| 102 | Connection to host.example.com 25 port [tcp/smtp] succeeded! |
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| 103 | .Ed |
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| 104 | .Pp |
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| 105 | -The port range was specified to limit the search to ports 20 \- 30. |
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| 106 | +The port range was specified to limit the search to ports 20 \- 30, and is |
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| 107 | +scanned by increasing order. |
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| 108 | +.Pp |
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| 109 | +You can also specify a list of ports to scan, for example: |
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| 110 | +.Bd -literal -offset indent |
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| 111 | +$ nc \-zv host.example.com 80 20 22 |
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| 112 | +nc: connect to host.example.com 80 (tcp) failed: Connection refused |
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| 113 | +nc: connect to host.example.com 20 (tcp) failed: Connection refused |
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| 114 | +Connection to host.example.com port [tcp/ssh] succeeded! |
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| 115 | +.Ed |
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| 116 | +.Pp |
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| 117 | +The ports are scanned by the order you given. |
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| 118 | .Pp |
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| 119 | Alternatively, it might be useful to know which server software |
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| 120 | is running, and which versions. |
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| 121 | @@ -455,6 +520,9 @@ Original implementation by *Hobbit* |
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| 122 | .br |
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| 123 | Rewritten with IPv6 support by |
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| 124 | .An Eric Jackson Aq ericj@monkey.org . |
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| 125 | +.br |
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| 126 | +Modified for Debian port by Aron Xu |
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| 127 | +.Aq aron@debian.org . |
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| 128 | .Sh CAVEATS |
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| 129 | UDP port scans using the |
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| 130 | .Fl uz |
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| 131 | diff --git a/netcat.c b/netcat.c |
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| 132 | index bf9940f..c938d11 100644 |
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| 133 | --- a/netcat.c |
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| 134 | +++ b/netcat.c |
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| 135 | @@ -88,6 +88,7 @@ |
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| 136 | #include <netdb.h> |
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| 137 | #include <poll.h> |
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| 138 | #include <signal.h> |
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| 139 | +#include <stddef.h> |
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| 140 | #include <stdarg.h> |
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| 141 | #include <stdio.h> |
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| 142 | #include <stdlib.h> |
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| 143 | @@ -115,6 +116,7 @@ |
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| 144 | #define UDP_SCAN_TIMEOUT 3 /* Seconds */ |
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| 145 | |
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| 146 | /* Command Line Options */ |
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| 147 | +int bflag; /* Allow Broadcast */ |
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| 148 | int Cflag = 0; /* CRLF line-ending */ |
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| 149 | int dflag; /* detached, no stdin */ |
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| 150 | unsigned int iflag; /* Interval Flag */ |
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| 151 | @@ -146,7 +148,7 @@ char *portlist[PORT_MAX+1]; |
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| 152 | char *unix_dg_tmp_socket; |
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| 153 | |
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| 154 | void atelnet(int, unsigned char *, unsigned int); |
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| 155 | -void build_ports(char *); |
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| 156 | +void build_ports(char **); |
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| 157 | void help(void); |
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| 158 | int local_listen(char *, char *, struct addrinfo); |
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| 159 | void readwrite(int); |
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| 160 | @@ -171,11 +173,14 @@ int |
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| 161 | main(int argc, char *argv[]) |
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| 162 | { |
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| 163 | int ch, s, ret, socksv; |
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| 164 | - char *host, *uport; |
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| 165 | + char *host, **uport; |
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| 166 | struct addrinfo hints; |
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| 167 | struct servent *sv; |
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| 168 | socklen_t len; |
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| 169 | - struct sockaddr_storage cliaddr; |
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| 170 | + union { |
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| 171 | + struct sockaddr_storage storage; |
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| 172 | + struct sockaddr_un forunix; |
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| 173 | + } cliaddr; |
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| 174 | char *proxy = NULL; |
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| 175 | const char *errstr, *proxyhost = "", *proxyport = NULL; |
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| 176 | struct addrinfo proxyhints; |
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| 177 | @@ -189,7 +194,7 @@ main(int argc, char *argv[]) |
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| 178 | sv = NULL; |
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| 179 | |
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| 180 | while ((ch = getopt(argc, argv, |
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| 181 | - "46CDdhI:i:jklnO:P:p:q:rSs:tT:UuV:vw:X:x:Zz")) != -1) { |
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| 182 | + "46bCDdhI:i:jklnO:P:p:q:rSs:tT:UuV:vw:X:x:Zz")) != -1) { |
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| 183 | switch (ch) { |
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| 184 | case '4': |
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| 185 | family = AF_INET; |
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| 186 | @@ -197,6 +202,13 @@ main(int argc, char *argv[]) |
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| 187 | case '6': |
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| 188 | family = AF_INET6; |
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| 189 | break; |
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| 190 | + case 'b': |
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| 191 | +# if defined(SO_BROADCAST) |
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| 192 | + bflag = 1; |
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| 193 | +# else |
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| 194 | + errx(1, "no broadcast frame support available"); |
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| 195 | +# endif |
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| 196 | + break; |
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| 197 | case 'U': |
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| 198 | family = AF_UNIX; |
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| 199 | break; |
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| 200 | @@ -342,35 +354,40 @@ main(int argc, char *argv[]) |
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| 201 | |
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| 202 | /* Cruft to make sure options are clean, and used properly. */ |
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| 203 | if (argv[0] && !argv[1] && family == AF_UNIX) { |
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| 204 | - if (uflag) |
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| 205 | - errx(1, "cannot use -u and -U"); |
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| 206 | # if defined(IPPROTO_DCCP) && defined(SOCK_DCCP) |
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| 207 | if (dccpflag) |
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| 208 | errx(1, "cannot use -Z and -U"); |
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| 209 | # endif |
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| 210 | host = argv[0]; |
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| 211 | uport = NULL; |
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| 212 | - } else if (!argv[0] && lflag) { |
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| 213 | - if (sflag) |
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| 214 | - errx(1, "cannot use -s and -l"); |
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| 215 | - if (zflag) |
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| 216 | - errx(1, "cannot use -z and -l"); |
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| 217 | - if (pflag) |
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| 218 | - uport=pflag; |
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| 219 | - } else if (!lflag && kflag) { |
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| 220 | - errx(1, "cannot use -k without -l"); |
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| 221 | - } else if (argv[0] && !argv[1]) { |
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| 222 | - if (!lflag) |
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| 223 | - usage(1); |
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| 224 | - uport = argv[0]; |
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| 225 | + } else if (argv[0] && !argv[1] && lflag) { |
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| 226 | + if (pflag) { |
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| 227 | + uport = &pflag; |
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| 228 | + host = argv[0]; |
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| 229 | + } else { |
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| 230 | + uport = argv; |
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| 231 | + host = NULL; |
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| 232 | + } |
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| 233 | + } else if (!argv[0] && lflag && pflag) { |
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| 234 | + uport = &pflag; |
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| 235 | host = NULL; |
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| 236 | } else if (argv[0] && argv[1]) { |
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| 237 | host = argv[0]; |
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| 238 | - uport = argv[1]; |
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| 239 | + uport = &argv[1]; |
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| 240 | } else |
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| 241 | usage(1); |
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| 242 | |
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| 243 | - |
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| 244 | + if (lflag) { |
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| 245 | + if (sflag) |
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| 246 | + errx(1, "cannot use -s and -l"); |
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| 247 | + if (zflag) |
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| 248 | + errx(1, "cannot use -z and -l"); |
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| 249 | + if (pflag) |
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| 250 | + /* This still does not work well because of getopt mess |
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| 251 | + errx(1, "cannot use -p and -l"); */ |
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| 252 | + uport = &pflag; |
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| 253 | + } else if (!lflag && kflag) |
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| 254 | + errx(1, "cannot use -k without -l"); |
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| 255 | |
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| 256 | /* Get name of temporary socket for unix datagram client */ |
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| 257 | if ((family == AF_UNIX) && uflag && !lflag) { |
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| 258 | @@ -448,7 +465,7 @@ main(int argc, char *argv[]) |
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| 259 | else |
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| 260 | s = unix_listen(host); |
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| 261 | } else |
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| 262 | - s = local_listen(host, uport, hints); |
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| 263 | + s = local_listen(host, *uport, hints); |
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| 264 | if (s < 0) |
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| 265 | err(1, NULL); |
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| 266 | |
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| 267 | @@ -457,7 +474,8 @@ main(int argc, char *argv[]) |
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| 268 | local = ":::"; |
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| 269 | else |
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| 270 | local = "0.0.0.0"; |
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| 271 | - fprintf(stderr, "Listening on [%s] (family %d, port %d)\n", |
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| 272 | + if (vflag && (family != AF_UNIX)) |
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| 273 | + fprintf(stderr, "Listening on [%s] (family %d, port %s)\n", |
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| 274 | host ?: local, |
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| 275 | family, |
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| 276 | *uport); |
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| 277 | @@ -490,13 +508,17 @@ main(int argc, char *argv[]) |
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| 278 | len = sizeof(cliaddr); |
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| 279 | connfd = accept(s, (struct sockaddr *)&cliaddr, |
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| 280 | &len); |
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| 281 | - if(vflag) { |
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| 282 | + if(vflag && family == AF_UNIX) { |
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| 283 | + fprintf(stderr, "Connection from \"%.*s\" accepted\n", |
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| 284 | + (len - (int)offsetof(struct sockaddr_un, sun_path)), |
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| 285 | + ((struct sockaddr_un*)&cliaddr)->sun_path); |
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| 286 | + } else if(vflag) { |
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| 287 | char *proto = proto_name(uflag, dccpflag); |
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| 288 | /* Don't look up port if -n. */ |
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| 289 | if (nflag) |
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| 290 | sv = NULL; |
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| 291 | else |
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| 292 | - sv = getservbyport(ntohs(atoi(uport)), |
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| 293 | + sv = getservbyport(ntohs(atoi(*uport)), |
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| 294 | proto); |
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| 295 | |
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| 296 | if (((struct sockaddr *)&cliaddr)->sa_family == AF_INET) { |
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| 297 | @@ -504,7 +526,7 @@ main(int argc, char *argv[]) |
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| 298 | inet_ntop(((struct sockaddr *)&cliaddr)->sa_family,&(((struct sockaddr_in *)&cliaddr)->sin_addr),dst,INET_ADDRSTRLEN); |
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| 299 | fprintf(stderr, "Connection from [%s] port %s [%s/%s] accepted (family %d, sport %d)\n", |
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| 300 | dst, |
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| 301 | - uport, |
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| 302 | + *uport, |
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| 303 | proto, |
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| 304 | sv ? sv->s_name : "*", |
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| 305 | ((struct sockaddr *)(&cliaddr))->sa_family, |
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| 306 | @@ -515,7 +537,7 @@ main(int argc, char *argv[]) |
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| 307 | inet_ntop(((struct sockaddr *)&cliaddr)->sa_family,&(((struct sockaddr_in6 *)&cliaddr)->sin6_addr),dst,INET6_ADDRSTRLEN); |
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| 308 | fprintf(stderr, "Connection from [%s] port %s [%s/%s] accepted (family %d, sport %d)\n", |
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| 309 | dst, |
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| 310 | - uport, |
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| 311 | + *uport, |
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| 312 | proto, |
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| 313 | sv ? sv->s_name : "*", |
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| 314 | ((struct sockaddr *)&cliaddr)->sa_family, |
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| 315 | @@ -523,17 +545,21 @@ main(int argc, char *argv[]) |
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| 316 | } |
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| 317 | else { |
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| 318 | fprintf(stderr, "Connection from unknown port %s [%s/%s] accepted (family %d, sport %d)\n", |
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| 319 | - uport, |
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| 320 | + *uport, |
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| 321 | proto, |
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| 322 | sv ? sv->s_name : "*", |
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| 323 | ((struct sockaddr *)(&cliaddr))->sa_family, |
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| 324 | ntohs(((struct sockaddr_in *)&cliaddr)->sin_port)); |
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| 325 | } |
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| 326 | } |
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| 327 | + if(!kflag) |
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| 328 | + close(s); |
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| 329 | readwrite(connfd); |
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| 330 | close(connfd); |
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| 331 | } |
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| 332 | |
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| 333 | + if (vflag && kflag) |
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| 334 | + fprintf(stderr, "Connection closed, listening again.\n"); |
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| 335 | if (kflag) |
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| 336 | continue; |
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| 337 | if (family != AF_UNIX) { |
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| 338 | @@ -641,6 +667,8 @@ unix_bind(char *path) |
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| 339 | return (-1); |
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| 340 | } |
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| 341 | |
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| 342 | + unlink(path); |
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| 343 | + |
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| 344 | if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { |
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| 345 | close(s); |
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| 346 | return (-1); |
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| 347 | @@ -662,8 +690,10 @@ unix_connect(char *path) |
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| 348 | if ((s = unix_bind(unix_dg_tmp_socket)) < 0) |
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| 349 | return (-1); |
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| 350 | } else { |
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| 351 | - if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) |
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| 352 | + if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) { |
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| 353 | + errx(1,"create unix socket failed"); |
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| 354 | return (-1); |
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| 355 | + } |
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| 356 | } |
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| 357 | (void)fcntl(s, F_SETFD, 1); |
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| 358 | |
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| 359 | @@ -674,9 +704,11 @@ unix_connect(char *path) |
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| 360 | sizeof(sun.sun_path)) { |
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| 361 | close(s); |
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| 362 | errno = ENAMETOOLONG; |
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| 363 | + warn("unix connect abandoned"); |
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| 364 | return (-1); |
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| 365 | } |
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| 366 | if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) { |
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| 367 | + warn("unix connect failed"); |
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| 368 | close(s); |
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| 369 | return (-1); |
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| 370 | } |
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| 371 | @@ -1105,22 +1137,23 @@ atelnet(int nfd, unsigned char *buf, unsigned int size) |
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| 372 | * that we should try to connect to. |
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| 373 | */ |
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| 374 | void |
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| 375 | -build_ports(char *p) |
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| 376 | +build_ports(char **p) |
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| 377 | { |
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| 378 | struct servent *sv; |
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| 379 | const char *errstr; |
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| 380 | char *n; |
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| 381 | int hi, lo, cp; |
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| 382 | int x = 0; |
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| 383 | + int i; |
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| 384 | |
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| 385 | char *proto = proto_name(uflag, dccpflag); |
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| 386 | - sv = getservbyname(p, proto); |
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| 387 | + sv = getservbyname(*p, proto); |
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| 388 | if (sv) { |
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| 389 | portlist[0] = calloc(1, PORT_MAX_LEN); |
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| 390 | if (portlist[0] == NULL) |
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| 391 | err(1, NULL); |
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| 392 | snprintf(portlist[0], PORT_MAX_LEN, "%d", ntohs(sv->s_port)); |
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| 393 | - } else if ((n = strchr(p, '-')) != NULL) { |
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| 394 | + } else if ((n = strchr(*p, '-')) != NULL) { |
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| 395 | *n = '\0'; |
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| 396 | n++; |
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| 397 | |
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| 398 | @@ -1128,9 +1161,9 @@ build_ports(char *p) |
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| 399 | hi = strtonum(n, 1, PORT_MAX, &errstr); |
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| 400 | if (errstr) |
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| 401 | errx(1, "port number %s: %s", errstr, n); |
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| 402 | - lo = strtonum(p, 1, PORT_MAX, &errstr); |
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| 403 | + lo = strtonum(*p, 1, PORT_MAX, &errstr); |
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| 404 | if (errstr) |
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| 405 | - errx(1, "port number %s: %s", errstr, p); |
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| 406 | + errx(1, "port number %s: %s", errstr, *p); |
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| 407 | |
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| 408 | if (lo > hi) { |
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| 409 | cp = hi; |
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| 410 | @@ -1160,10 +1193,12 @@ build_ports(char *p) |
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| 411 | } |
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| 412 | } |
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| 413 | } else { |
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| 414 | - hi = strtonum(p, 1, PORT_MAX, &errstr); |
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| 415 | + hi = strtonum(*p, 1, PORT_MAX, &errstr); |
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| 416 | if (errstr) |
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| 417 | - errx(1, "port number %s: %s", errstr, p); |
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| 418 | - portlist[0] = strdup(p); |
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| 419 | + errx(1, "port number %s: %s", errstr, *p); |
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| 420 | + for (i=0;p[i];i++) { |
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| 421 | + portlist[i] = strdup(p[i]); |
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| 422 | + } |
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| 423 | if (portlist[0] == NULL) |
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| 424 | err(1, NULL); |
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| 425 | } |
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| 426 | @@ -1198,6 +1233,13 @@ set_common_sockopts(int s) |
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| 427 | { |
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| 428 | int x = 1; |
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| 429 | |
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| 430 | +# if defined(SO_BROADCAST) |
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| 431 | + if (bflag) { |
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| 432 | + if (setsockopt(s, IPPROTO_TCP, SO_BROADCAST, |
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| 433 | + &x, sizeof(x)) == -1) |
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| 434 | + err(1, NULL); |
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| 435 | + } |
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| 436 | +# endif |
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| 437 | # if defined(TCP_MD5SIG) |
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| 438 | if (Sflag) { |
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| 439 | if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG, |
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| 440 | @@ -1293,6 +1335,7 @@ help(void) |
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| 441 | fprintf(stderr, "\tCommand Summary:\n\ |
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| 442 | \t-4 Use IPv4\n\ |
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| 443 | \t-6 Use IPv6\n\ |
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| 444 | + \t-b Allow broadcast\n\ |
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| 445 | \t-C Send CRLF as line-ending\n\ |
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| 446 | \t-D Enable the debug socket option\n\ |
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| 447 | \t-d Detach from stdin\n\ |
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| 448 | @@ -1329,7 +1372,7 @@ void |
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| 449 | usage(int ret) |
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| 450 | { |
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| 451 | fprintf(stderr, |
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| 452 | - "usage: nc [-46CDdhjklnrStUuvZz] [-I length] [-i interval] [-O length]\n" |
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| 453 | + "usage: nc [-46bCDdhjklnrStUuvZz] [-I length] [-i interval] [-O length]\n" |
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| 454 | "\t [-P proxy_username] [-p source_port] [-q seconds] [-s source]\n" |
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| 455 | "\t [-T toskeyword] [-V rtable] [-w timeout] [-X proxy_protocol]\n" |
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| 456 | "\t [-x proxy_address[:port]] [destination] [port]\n"); |
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| 457 | -- |
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