doc: add the description of aspath prepend action

2 files changed, 23 insertions, 8 deletions

diff --git a/docs/sources/cli-command-syntax.md b/docs/sources/cli-command-syntax.md
index 730d712e..6faac956 100644
--- a/docs/sources/cli-command-syntax.md
+++ b/docs/sources/cli-command-syntax.md
@@ -273,7 +273,7 @@ If you want to remove one element(community) of CommunitySet, to specify a addre
 #### - example
 If you want to add the RoutePolicy：
 ```shell
-% gobgp policy routepolicy add policy1 state1 --c-prefix=ps1 --c-neighbor=ns1 --c-aspath=ass1 --c-community=cs1 --c-aslen=eq,3 --c-option=all --a-route=reject --a-community=ADD[65100:20] --a-med=+100
+% gobgp policy routepolicy add policy1 state1 --c-prefix=ps1 --c-neighbor=ns1 --c-aspath=ass1 --c-community=cs1 --c-aslen=eq,3 --c-option=all --a-route=reject --a-community=ADD[65100:20] --a-med=+100 --a-asprepend=65100,10
 ```
 However, it is not necessary to specify all of the options at once.
 
@@ -296,15 +296,16 @@ The following options can be specified in the policy subcommand:
 |-       |c-prefix    |specify the name that added prefix set in PrefixSet subcommand      |
 |-       |c-neighbor  |specify the name that added neighbor set in NeighborSet subcommand  |
 |-       |c-aspath    |specify the name that added as path set in AsPathSet subcommand     |
-|-       |c-community |pecify the name that added community set in CommunitySet subcommand |
+|-       |c-community |specify the name that added community set in CommunitySet subcommand|
 |-       |c-aslen     |specify the operator(eq, ge, le) and value(numric)                  |
 |-       |c-option    |specify the match option(any, all, invert)                          |
 
   - options of action
 
-| short  |long        | description                                                                 |
-|--------|------------|-----------------------------------------------------------------------------|
-|-       |a-route     |specify the action(accept, reject) of the route that match to the conditions |
-|-       |a-community |specify the community operation of the route that match to the conditions    |
-|-       |a-med       |specify the med operation of the route that match to the conditions          |
+| short  |long        | description                                                                                                   |
+|--------|------------|---------------------------------------------------------------------------------------------------------------|
+|-       |a-route     |specify the action(accept, reject) of the route that match to the conditions                                   |
+|-       |a-community |specify the community operation of the route that match to the conditions                                      |
+|-       |a-med       |specify the med operation of the route that match to the conditions                                            |
+|-       |a-asprepend |specify a combination of an AS number and repeat count(e.g. 65100,10) to prepend if the path matches conditions|
 
diff --git a/docs/sources/filter-detail.md b/docs/sources/filter-detail.md
index d4251c1a..6ae42a0e 100644
--- a/docs/sources/filter-detail.md
+++ b/docs/sources/filter-detail.md
@@ -20,6 +20,7 @@ A action part is below:
  - accept or reject
  - add/replace/remove community or remove all communities
  - add/subtract or replace MED value
+ - prepend AS number in the AS_PATH attribute
 
 
 GoBGP's configuration file has two parts named DefinedSets and PolicyDefinitionList as its policy configuration.
@@ -365,6 +366,9 @@ You can write condition and action under StatementList.
     [PolicyDefinitionList.StatementList.Actions.BgpActions.SetCommunity]
       Communities = ["65100:20"]
       Options = "ADD"
+    [PolicyDefinitionList.StatementList.Actions.BgpActions.SetAsPathPrepend]
+      As = "65005"
+      RepeatN = 5
  ```
 
  The elements of PolicyDefinitionList are as follows:
@@ -425,6 +429,13 @@ You can write condition and action under StatementList.
  | Communities | communities used to manipulate the route's community accodriong to Options below | "65100:20"    |
  | Options     | operator to manipulate Community attribute in the route                          | "ADD"       |
 
+  - PolicyDefinitionList.StatementList.Actions.BgpActions.SetAsPathPrepend
+  
+ | Element | Description                                                                                           | Example |
+ |---------|-------------------------------------------------------------------------------------------------------|---------|
+ | As      | AS number to prepend. You can use "last-as" to prepend the leftmost AS number in the aspath attribute.| "65100" |
+ | RepeatN | repeat count to prepend AS                                                                            |    5    |
+
  <br>
 
 ##### Examples
@@ -514,7 +525,7 @@ You can write condition and action under StatementList.
     - AsPathSet: *aspath1*
     - AsPath length: *equal 2*
 
-  - If a route matches all these conditions, the route is accepted and added community "65100:20" and subtract 200 from med value.
+  - If a route matches all these conditions, the route is accepted and added community "65100:20" and subtracted 200 from med value and prepended 65005 five times in its AS_PATH attribute.
 
  ```
  # example 4
@@ -539,6 +550,9 @@ You can write condition and action under StatementList.
  [PolicyDefinitionList.StatementList.Actions.BgpActions.SetCommunity]
  Communities = ["65100:20"]
  Options = "ADD"
+ [PolicyDefinitionList.StatementList.Actions.BgpActions.SetAsPathPrepend]
+ As = "65005"
+ RepeatN = 5
  ```