Propagate 'last-modified' and 'etag' fields while proxying.

But does it work?

html.c

@@ -2796,7 +2796,8 @@ xs_str *html_notifications(snac *user, int skip, int show)
 
 
 int html_get_handler(const xs_dict *req, const char *q_path,
-                     char **body, int *b_size, char **ctype, xs_str **etag)
+                     char **body, int *b_size, char **ctype,
+                     xs_str **etag, xs_str **last_modified)
 {
     const char *accept = xs_dict_get(req, "accept");
     int status = HTTP_STATUS_NOT_FOUND;
@@ -3227,6 +3228,11 @@ int html_get_handler(const xs_dict *req, const char *q_path,
 
             if (valid_status(status)) {
                 const char *ct = xs_dict_get(rsp, "content-type");
+                const char *lm = xs_dict_get(rsp, "last-modified");
+                const char *et = xs_dict_get(rsp, "etag");
+
+                if (lm) *last_modified = xs_dup(lm);
+                if (et) *etag = xs_dup(et);
 
                 /* find the content-type in the static mime types,
                    and return that value instead of ct, which will

httpd.c

@@ -278,6 +278,7 @@ void httpd_connection(FILE *f)
     xs *q_path   = NULL;
     xs *payload  = NULL;
     xs *etag     = NULL;
+    xs *last_modified = NULL;
     int p_size   = 0;
     const char *p;
     int fcgi_id;
@@ -329,7 +330,7 @@ void httpd_connection(FILE *f)
 #endif /* NO_MASTODON_API */
 
         if (status == 0)
-            status = html_get_handler(req, q_path, &body, &b_size, &ctype, &etag);
+            status = html_get_handler(req, q_path, &body, &b_size, &ctype, &etag, &last_modified);
     }
     else
     if (strcmp(method, "POST") == 0) {
@@ -423,6 +424,8 @@ void httpd_connection(FILE *f)
 
     if (!xs_is_null(etag))
         headers = xs_dict_append(headers, "etag", etag);
+    if (!xs_is_null(last_modified))
+        headers = xs_dict_append(headers, "last-modified", last_modified);
 
     /* if there are any additional headers, add them */
     const xs_dict *more_headers = xs_dict_get(srv_config, "http_headers");

snac.h

@@ -349,7 +349,9 @@ xs_str *html_timeline(snac *user, const xs_list *list, int read_only,
                       const char *title, const char *page, int utl, const char *error);
 
 int html_get_handler(const xs_dict *req, const char *q_path,
-                     char **body, int *b_size, char **ctype, xs_str **etag);
+                     char **body, int *b_size, char **ctype,
+                     xs_str **etag, xs_str **last_modified);
+
 int html_post_handler(const xs_dict *req, const char *q_path,
                       char *payload, int p_size,
                       char **body, int *b_size, char **ctype);