Mail: POP3 pipelining support.

The change is mostly the same as the SMTP one (04e43d03e153 and 3f5d0af4e40a),
and ensures that nginx is able to properly handle or reject multiple POP3
commands, as required by the PIPELINING capability (RFC 2449).  The s->cmd
field is not really used and set for consistency.

src/mail/ngx_mail_parse.c

@@ -21,6 +21,8 @@ ngx_mail_pop3_parse_command(ngx_mail_session_t *s)
     ngx_str_t  *arg;
     enum {
         sw_start = 0,
+        sw_command,
+        sw_invalid,
         sw_spaces_before_argument,
         sw_argument,
         sw_almost_done
@@ -35,8 +37,14 @@ ngx_mail_pop3_parse_command(ngx_mail_session_t *s)
 
         /* POP3 command */
         case sw_start:
+            s->cmd_start = p;
+            state = sw_command;
+
+            /* fall through */
+
+        case sw_command:
             if (ch == ' ' || ch == CR || ch == LF) {
-                c = s->buffer->start;
+                c = s->cmd_start;
 
                 if (p - c == 4) {
 
@@ -85,6 +93,9 @@ ngx_mail_pop3_parse_command(ngx_mail_session_t *s)
                     goto invalid;
                 }
 
+                s->cmd.data = s->cmd_start;
+                s->cmd.len = p - s->cmd_start;
+
                 switch (ch) {
                 case ' ':
                     state = sw_spaces_before_argument;
@@ -104,6 +115,9 @@ ngx_mail_pop3_parse_command(ngx_mail_session_t *s)
 
             break;
 
+        case sw_invalid:
+            goto invalid;
+
         case sw_spaces_before_argument:
             switch (ch) {
             case ' ':
@@ -205,10 +219,22 @@ done:
 
 invalid:
 
-    s->state = sw_start;
+    s->state = sw_invalid;
     s->arg_start = NULL;
 
-    return NGX_MAIL_PARSE_INVALID_COMMAND;
+    /* skip invalid command till LF */
+
+    for ( /* void */ ; p < s->buffer->last; p++) {
+        if (*p == LF) {
+            s->state = sw_start;
+            s->buffer->pos = p + 1;
+            return NGX_MAIL_PARSE_INVALID_COMMAND;
+        }
+    }
+
+    s->buffer->pos = p;
+
+    return NGX_AGAIN;
 }
 
 

src/mail/ngx_mail_pop3_handler.c

@@ -262,6 +262,10 @@ ngx_mail_pop3_auth_state(ngx_event_t *rev)
         }
     }
 
+    if (s->buffer->pos < s->buffer->last) {
+        s->blocked = 1;
+    }
+
     switch (rc) {
 
     case NGX_DONE:
@@ -283,11 +287,14 @@ ngx_mail_pop3_auth_state(ngx_event_t *rev)
     case NGX_OK:
 
         s->args.nelts = 0;
-        s->buffer->pos = s->buffer->start;
-        s->buffer->last = s->buffer->start;
+
+        if (s->buffer->pos == s->buffer->last) {
+            s->buffer->pos = s->buffer->start;
+            s->buffer->last = s->buffer->start;
+        }
 
         if (s->state) {
-            s->arg_start = s->buffer->start;
+            s->arg_start = s->buffer->pos;
         }
 
         if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
@@ -400,6 +407,8 @@ ngx_mail_pop3_stls(ngx_mail_session_t *s, ngx_connection_t *c)
     if (c->ssl == NULL) {
         sslcf = ngx_mail_get_module_srv_conf(s, ngx_mail_ssl_module);
         if (sslcf->starttls) {
+            s->buffer->pos = s->buffer->start;
+            s->buffer->last = s->buffer->start;
             c->read->handler = ngx_mail_starttls_handler;
             return NGX_OK;
         }

src/mail/ngx_mail_proxy_module.c

@@ -327,6 +327,10 @@ ngx_mail_proxy_pop3_handler(ngx_event_t *rev)
         c->log->action = NULL;
         ngx_log_error(NGX_LOG_INFO, c->log, 0, "client logged in");
 
+        if (s->buffer->pos < s->buffer->last) {
+            ngx_post_event(c->write, &ngx_posted_events);
+        }
+
         ngx_mail_proxy_handler(s->connection->write);
 
         return;