Mail: configurable socket buffer sizes.

The "rcvbuf" and "sndbuf" parameters are now supported by
the "listen" directive.
diff --git a/src/mail/ngx_mail.c b/src/mail/ngx_mail.c
index 9e560bb..5fd5fa0 100644
--- a/src/mail/ngx_mail.c
+++ b/src/mail/ngx_mail.c
@@ -333,6 +333,8 @@
             ls->log.handler = ngx_accept_log_error;
 
             ls->backlog = addr[i].opt.backlog;
+            ls->rcvbuf = addr[i].opt.rcvbuf;
+            ls->sndbuf = addr[i].opt.sndbuf;
 
             ls->keepalive = addr[i].opt.so_keepalive;
 #if (NGX_HAVE_KEEPALIVE_TUNABLE)
diff --git a/src/mail/ngx_mail.h b/src/mail/ngx_mail.h
index 6002508..6ecfefc 100644
--- a/src/mail/ngx_mail.h
+++ b/src/mail/ngx_mail.h
@@ -46,6 +46,8 @@
     int                     tcp_keepcnt;
 #endif
     int                     backlog;
+    int                     rcvbuf;
+    int                     sndbuf;
 } ngx_mail_listen_t;
 
 
diff --git a/src/mail/ngx_mail_core_module.c b/src/mail/ngx_mail_core_module.c
index b974d90..276b8ee 100644
--- a/src/mail/ngx_mail_core_module.c
+++ b/src/mail/ngx_mail_core_module.c
@@ -295,7 +295,7 @@
 {
     ngx_mail_core_srv_conf_t  *cscf = conf;
 
-    ngx_str_t                  *value;
+    ngx_str_t                  *value, size;
     ngx_url_t                   u;
     ngx_uint_t                  i, m;
     ngx_mail_listen_t          *ls;
@@ -350,6 +350,8 @@
 
     ls->socklen = u.socklen;
     ls->backlog = NGX_LISTEN_BACKLOG;
+    ls->rcvbuf = -1;
+    ls->sndbuf = -1;
     ls->wildcard = u.wildcard;
     ls->ctx = cf->ctx;
 
@@ -398,6 +400,38 @@
             continue;
         }
 
+        if (ngx_strncmp(value[i].data, "rcvbuf=", 7) == 0) {
+            size.len = value[i].len - 7;
+            size.data = value[i].data + 7;
+
+            ls->rcvbuf = ngx_parse_size(&size);
+            ls->bind = 1;
+
+            if (ls->rcvbuf == NGX_ERROR) {
+                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                                   "invalid rcvbuf \"%V\"", &value[i]);
+                return NGX_CONF_ERROR;
+            }
+
+            continue;
+        }
+
+        if (ngx_strncmp(value[i].data, "sndbuf=", 7) == 0) {
+            size.len = value[i].len - 7;
+            size.data = value[i].data + 7;
+
+            ls->sndbuf = ngx_parse_size(&size);
+            ls->bind = 1;
+
+            if (ls->sndbuf == NGX_ERROR) {
+                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                                   "invalid sndbuf \"%V\"", &value[i]);
+                return NGX_CONF_ERROR;
+            }
+
+            continue;
+        }
+
         if (ngx_strncmp(value[i].data, "ipv6only=o", 10) == 0) {
 #if (NGX_HAVE_INET6 && defined IPV6_V6ONLY)
             size_t  len;