iptables(8) -A INPUT -s 192.168.1.10 -p tcp --dport 22 -j ACCEPT
administration tool for IPv4 packet filtering and NAT
-A, --append chain rule-specification
       Append one or more rules to the end of the selected chain.  When  the  source  and/or  destination
       names  resolve  to  more  than  one  address,  a  rule  will  be  added  for each possible address
       combination.
[!] -s, --source address[/mask][,...]
       Source specification. Address can be either a network name, a hostname, a network IP address (with
       /mask),  or a plain IP address. Hostnames will be resolved once only, before the rule is submitted
       to the kernel.  Please note that specifying any name to be resolved with a remote  query  such  as
       DNS is a really bad idea.  The mask can be either a network mask or a plain number, specifying the
       number of 1's at the left side of the  network  mask.   Thus,  a  mask  of  24  is  equivalent  to
       255.255.255.0.   A "!" argument before the address specification inverts the sense of the address.
       The flag --src is an alias for this option.  Multiple addresses can be specified,  but  this  will
       expand  to  multiple rules (when adding with -A), or will cause multiple rules to be deleted (with
       -D).
[!] -p, --protocol protocol
       The protocol of the rule or of the packet to check.  The specified protocol can  be  one  of  tcp,
       udp,  udplite,  icmp,  esp,  ah,  sctp or the special keyword "all", or it can be a numeric value,
       representing one of these protocols or a different one.  A protocol name  from  /etc/protocols  is
       also allowed.  A "!" argument before the protocol inverts the test.  The number zero is equivalent
       to all. "all" will match with all protocols and is taken as default when this option is omitted.
[!] --destination-port,--dport port[:port]
       Destination port or port range specification.  The flag --dport is a  convenient  alias  for  this
       option.
-j, --jump target
       This  specifies the target of the rule; i.e., what to do if the packet matches it.  The target can
       be a user-defined chain (other than the one this rule is in), one of the special  builtin  targets
       which  decide the fate of the packet immediately, or an extension (see EXTENSIONS below).  If this
       option is omitted in a rule (and -g is not used), then matching the rule will have  no  effect  on
       the packet's fate, but the counters on the rule will be incremented.
source manpages: iptables