.TH FORCE_BIND "1"
.SH NAME
FORCE_BIND
.SH AUTHOR
Catalin(ux) M. BOIE \- catab at embedromix dot ro
.SH DESCRIPTION
Force an application to bind on a specific IP and/or port. Plus forcing setsockopt calls on the socket. Works with both IPv4 and IPv6.
.TP
It is useful if you have a binary application without sources and without the possibility to configure address or port to bind to.
.SH LICENSE
GPLv3
.SH HOW IT WORKS
force_bind is a shared object that is loaded with LD_PRELOAD and hooks 'bind' function. Forcing an IP/port to bind to is done with environments variables.
.SH EXAMPLES
0. Output debug stuff in a log file (for debugging):
.TP
\fB	export FORCE_NET_VERBOSE=999
.TP
\fB	export FORCE_NET_LOG="xxx.log"
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
1. Force bind to 127.0.0.1, port 33, verbose operations:
.TP
\fB	export FORCE_NET_VERBOSE=1
.TP
\fB	export FORCE_BIND_ADDRESS_V4=127.0.0.1
.TP
\fB	export FORCE_BIND_PORT_V4=33
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
2. Force binding to 127.0.0.2, port unchanged
.TP
\fB	export FORCE_BIND_ADDRESS_V4=127.0.0.2
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
3. Force binding to ::1 (IPv6), port unchanged
.TP
\fB	export FORCE_BIND_ADDRESS_V6=::1
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
4. Changing TOS on all sockets to 30
.TP
\fB	export FORCE_NET_TOS=30
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
5. Force Keep alive to 60 seconds:
.TP
\fB	export FORCE_NET_KA=60
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
6. Force MSS to 1400
.TP
\fB	export FORCE_NET_MSS=1400
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
7. Force bandwidth to 1000 bytes/s for _all_ connections, cumulated
.TP
\fB	export FORCE_NET_BW=1000
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
8. Force bandwidth to 20000 bytes/s per socket
.TP
\fB	export FORCE_NET_BW_PER_SOCKET=20000
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
9. Force REUSEADDR
.TP
\fB	export FORCE_NET_REUSEADDR=1
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
10. Force NODELAY
.TP
\fB	export FORCE_NET_NODELAY=1
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
11. Force client connections (for example 'telnet', 'ssh', 'firefox') to connect from a specified address, not the auto selected one:
.TP
\fB	export FORCE_NET_VERBOSE=1
.TP
\fB	export FORCE_BIND_ADDRESS_V4=127.0.0.2
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
12. Set a FLOWINFO (flow label + class) for a client connection:
.TP
\fB	export FORCE_NET_VERBOSE=1
.TP
\fB	export FORCE_NET_FLOWINFO=0x7812345 # class 0x78, label 0x12345
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
13. Force FWMARK on a connection (only root can do it):
.TP
\fB	export FORCE_NET_VERBOSE=1
.TP
\fB	export FORCE_NET_FWMARK=0x1234
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
14. Force priority (between 0 and 6 for non-root users). You can use 'tc' command from iproute to set-up 'prio' qdisc and to assign prio to queues:
.TP
\fB	# 0. setup
.TP
\fB	export FORCE_NET_VERBOSE=1
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	# 1. Make sure you have a 'prio' qdisc attached to eth0, for example:
.TP
\fB	tc qdisc add ev eth0 root handle 1: prio
.TP
\fB	# 2. Assign applications to classed (bands):
.TP
\fB	export FORCE_NET_PRIO=6 # interactive, band 0
.TP
\fB	your_voip_program_here
.TP
\fB	export FORCE_NET_PRIO=0 # best effort, band 1
.TP
\fB	your_mail_program_here
.TP
\fB	export FORCE_NET_PRIO=2 # bulk, band 2
.TP
\fB	your_remote_backup_program_here
.TP
\fB	# 3. Run tc statistics so you can see the classification:
.TP
\fB	tc -s class show dev eth0
.TP
15. Deny binding to any IPv4 sockets. The bind syscall will return -1 and errno will be set to EACCES.
.TP
\fB	export FORCE_NET_VERBOSE=1
.TP
\fB	export FORCE_BIND_ADDRESS_V4=deny
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here
.TP
16. Silent fake binding to any IPv6 sockets. The bind will return success, but will never accept any connection.
.TP
\fB	export FORCE_NET_VERBOSE=1
.TP
\fB	export FORCE_BIND_ADDRESS_V6=fake
.TP
\fB	export LD_PRELOAD=${LD_PRELOAD}:/usr/lib/force_bind.so
.TP
\fB	your_program_here