Router: client IP address replacement.

This commit introduces the replacement of the client address based on the value
of a specified HTTP header.  This is intended for use when Unit is placed
behind a reverse proxy like nginx or a CDN.

You must specify the source addresses of the trusted proxies.  This can be
accomplished with any valid IP pattern supported by Unit's match block:

["10.0.0.1", "10.4.0.0/16", "!192.168.1.1"]

The feature is configured per listener.

The client address replacement functionality only operates when there is a
source IP match and the specified header is present.  Typically this would be
an 'X-Forwarded-For' header.

{
    "listeners": {
        "127.0.0.1:8080": {
            "client_ip": {
                "header": "X-Forwarded-For",
                "source": [
                    "10.0.0.0/8"
                ]
            },
            "pass": "applications/my_app"
        },
    }
}

If a request occurs and Unit receives a header like below:

"X-Forwarded-For: 84.123.23.23"

By default, Unit trusts the last rightmost IP in the header, so REMOTE_ADDR
will be set to 84.123.23.23 if the connection originated from 10.0.0.0/8.

If Unit runs behind consecutive reverse proxies and receives a header similar
to the following:

"X-Forwarded-For: 84.123.23.23, 10.0.0.254"

You will need to enable "recursive" checking, which walks the header from
last address to first and chooses the first non-trusted address it finds.

{
    "listeners": {
        "127.0.0.1:8080": {
            "client_ip": {
                "header": "X-Forwarded-For",
                "source": [
                    "10.0.0.0/8"
                ]
                "recursive": true,
            },
            "pass": "applications/my_app"
        },
    }
}

If a connection from 10.0.0.0/8 occurs, the chain is walked.  Here, 10.0.0.254
is also a trusted address so the client address will be replaced with
84.123.23.23.

If all IP addresses in the header are trusted, the client address is set to
the first address in the header:

If 10.0.0.0/8 is trusted and "X-Forwarded-For: 10.0.0.3, 10.0.0.2, 10.0.0.1",
the client address will be replaced with 10.0.0.3.

1 files changed, 4 insertions, 8 deletions

diff --git a/src/nxt_http_route.c b/src/nxt_http_route.c
index b330796f..cff69f96 100644
--- a/src/nxt_http_route.c
+++ b/src/nxt_http_route.c
@@ -135,12 +135,12 @@ typedef struct {
 } nxt_http_route_table_t;
 
 
-typedef struct {
+struct nxt_http_route_addr_rule_s {
     /* The object must be the first field. */
     nxt_http_route_object_t        object:8;
     uint32_t                       items;
     nxt_http_route_addr_pattern_t  addr_pattern[0];
-} nxt_http_route_addr_rule_t;
+};
 
 
 typedef union {
@@ -194,8 +194,6 @@ static nxt_http_route_ruleset_t *nxt_http_route_ruleset_create(nxt_task_t *task,
 static nxt_http_route_rule_t *nxt_http_route_rule_name_create(nxt_task_t *task,
     nxt_mp_t *mp, nxt_conf_value_t *rule_cv, nxt_str_t *name,
     nxt_bool_t case_sensitive, nxt_http_route_encoding_t encoding);
-static nxt_http_route_addr_rule_t *nxt_http_route_addr_rule_create(
-    nxt_task_t *task, nxt_mp_t *mp, nxt_conf_value_t *cv);
 static nxt_http_route_rule_t *nxt_http_route_rule_create(nxt_task_t *task,
     nxt_mp_t *mp, nxt_conf_value_t *cv, nxt_bool_t case_sensitive,
     nxt_http_route_pattern_case_t pattern_case,
@@ -237,8 +235,6 @@ static nxt_int_t nxt_http_route_table(nxt_http_request_t *r,
     nxt_http_route_table_t *table);
 static nxt_int_t nxt_http_route_ruleset(nxt_http_request_t *r,
     nxt_http_route_ruleset_t *ruleset);
-static nxt_int_t nxt_http_route_addr_rule(nxt_http_request_t *r,
-    nxt_http_route_addr_rule_t *addr_rule, nxt_sockaddr_t *sockaddr);
 static nxt_int_t nxt_http_route_rule(nxt_http_request_t *r,
     nxt_http_route_rule_t *rule);
 static nxt_int_t nxt_http_route_header(nxt_http_request_t *r,
@@ -940,7 +936,7 @@ nxt_http_route_rule_create(nxt_task_t *task, nxt_mp_t *mp,
 }
 
 
-static nxt_http_route_addr_rule_t *
+nxt_http_route_addr_rule_t *
 nxt_http_route_addr_rule_create(nxt_task_t *task, nxt_mp_t *mp,
      nxt_conf_value_t *cv)
 {
@@ -1927,7 +1923,7 @@ nxt_http_route_addr_pattern_match(nxt_http_route_addr_pattern_t *p,
 }
 
 
-static nxt_int_t
+nxt_int_t
 nxt_http_route_addr_rule(nxt_http_request_t *r,
     nxt_http_route_addr_rule_t *addr_rule, nxt_sockaddr_t *sa)
 {