[nginx] Add abstract socket support on Linux

[Bjørnar Ness]

# HG changeset patch
# User Bjornar Ness <bjornar.ness at gmail.com>
# Date 1552311828 -3600
#      Mon Mar 11 14:43:48 2019 +0100
# Node ID 9bf37762c5066b2f0ec3e6a312d97c86c4fdba18
# Parent  c74904a1702135f673a275bd0d36f010a3bfb89a
Add abstract socket support on Linux

This patch adds abstract socket support for Linux, making it possible
to both listen and connect to abstract socket:

server {
  listen unix:@abstract-socket;
}

This is convenient for ephemeral sockets for i.e fastcgi/uwsgi

diff -r c74904a17021 -r 9bf37762c506 src/core/ngx_connection.c
--- a/src/core/ngx_connection.c    Sat Mar 09 03:03:56 2019 +0300
+++ b/src/core/ngx_connection.c    Mon Mar 11 14:43:48 2019 +0100
@@ -625,7 +625,12 @@

 #if (NGX_HAVE_UNIX_DOMAIN)

-            if (ls[i].sockaddr->sa_family == AF_UNIX) {
+            if (ls[i].sockaddr->sa_family == AF_UNIX
+#if (NGX_LINUX)
+                && ls[i].addr_text.data[sizeof("unix:") - 1] != '@'
+#endif
+               )
+            {
                 mode_t   mode;
                 u_char  *name;

@@ -1069,6 +1074,9 @@
 #if (NGX_HAVE_UNIX_DOMAIN)

         if (ls[i].sockaddr->sa_family == AF_UNIX
+#if (NGX_LINUX)
+            && ls[i].addr_text.data[sizeof("unix:") - 1] != '@'
+#endif
             && ngx_process <= NGX_PROCESS_MASTER
             && ngx_new_binary == 0)
         {
diff -r c74904a17021 -r 9bf37762c506 src/core/ngx_cycle.c
--- a/src/core/ngx_cycle.c    Sat Mar 09 03:03:56 2019 +0300
+++ b/src/core/ngx_cycle.c    Mon Mar 11 14:43:48 2019 +0100
@@ -709,7 +709,12 @@

 #if (NGX_HAVE_UNIX_DOMAIN)

-        if (ls[i].sockaddr->sa_family == AF_UNIX) {
+        if (ls[i].sockaddr->sa_family == AF_UNIX
+#if (NGX_LINUX)
+            && ls[i].addr_text.data[sizeof("unix:") - 1] != '@'
+#endif
+           )
+        {
             u_char  *name;

             name = ls[i].addr_text.data + sizeof("unix:") - 1;
diff -r c74904a17021 -r 9bf37762c506 src/core/ngx_inet.c
--- a/src/core/ngx_inet.c    Sat Mar 09 03:03:56 2019 +0300
+++ b/src/core/ngx_inet.c    Mon Mar 11 14:43:48 2019 +0100
@@ -242,6 +242,9 @@
         if (socklen <= (socklen_t) offsetof(struct sockaddr_un, sun_path)) {
             p = ngx_snprintf(text, len, "unix:%Z");

+        } else if (saun->sun_path[0] == '\0') {
+            p = ngx_snprintf(text, len, "unix:@%s%Z", &saun->sun_path[1]);
+
         } else {
             n = ngx_strnlen((u_char *) saun->sun_path,
                             socklen - offsetof(struct sockaddr_un, sun_path));
@@ -744,6 +747,13 @@
     saun->sun_family = AF_UNIX;
     (void) ngx_cpystrn((u_char *) saun->sun_path, path, len);

+#if (NGX_LINUX)
+    if (path[0] == '@') {
+        saun->sun_path[0] = '\0';
+        u->socklen = sizeof(sa_family_t) + strlen(path);
+    }
+#endif
+
     u->addrs = ngx_pcalloc(pool, sizeof(ngx_addr_t));
     if (u->addrs == NULL) {
         return NGX_ERROR;
@@ -765,6 +775,13 @@
     u->addrs[0].name.len = len + 4;
     u->addrs[0].name.data = u->url.data;

+#if (NGX_LINUX)
+    if (path[0] == '@') {
+        saun->sun_path[0] = '\0';
+        u->addrs[0].socklen = sizeof(sa_family_t) + strlen(path);
+    }
+#endif
+
     return NGX_OK;

 #else