Fix header table corruption

We had a bug during the suffix match in function
`tfw_http_search_cookie()`, before comparing
the name we store current chunk `t = *chunk`, then
modify and compare the chunk, after we rostore the
chunk `*chunk = t;` that leads to header corruption,
because macros `TFW_STR_EQ_CSTR` may assign new
address to `chunk`, therefore restoration happens to
a newly assigned adress instead of original adress in
`chunk`. Fixed by storing address to temporary
variable and then restore `data` and `len` by this
adress.

`__tfw_str_eq_cstr` rewritten to inline function.
Inline functions is more clear, less error prone and
suitable in this case, because we don't need to define
tmp vars and explicitly save values, only move `chunk`
pointer forward. Generated assembly will be the same.

Author: const-t

fw/http_match.c

@@ -876,6 +876,31 @@ tfw_http_verify_hdr_field(tfw_http_match_fld_t field, const char **hdr_name,
 	return 0;
 }
 
+/* Simple version of tfw_str_eq_cstr. */
+static bool __always_inline
+__tfw_str_eq_cstr(const char *cstr, unsigned long clen, TfwStr **pos,
+		  const TfwStr *end)
+{
+	TfwStr *chunk = *pos;
+
+	while (chunk != end) {
+		int len = min(clen, chunk->len);
+
+		if (memcmp_fast(cstr, chunk->data, len))
+			break;
+
+		cstr += len;
+		clen -= len;
+		if (!clen)
+			break;
+		chunk++;
+	}
+
+	*pos = chunk;
+
+	return !clen;
+}
+
 /*
  * Search for cookie in `Set-Cookie`/`Cookie` header value @cookie
  * and save the cookie value into @val.
@@ -902,26 +927,6 @@ tfw_http_search_cookie(const char *cstr, unsigned long clen,
 {
 	TfwStr *chunk;
 
-/* Simple version of tfw_str_eq_cstr. */
-#define TFW_STR_EQ_CSTR(end)						\
-({									\
-	const char *tmp_cstr = cstr;					\
-	unsigned long tmp_clen = clen;					\
-									\
-	while (chunk != end) {						\
-		int len = min(tmp_clen, chunk->len);			\
-		if (memcmp_fast(tmp_cstr, chunk->data, len))		\
-			break;						\
-									\
-		tmp_cstr += len;					\
-		tmp_clen -= len;					\
-		if (!tmp_clen)						\
-			break;						\
-		chunk++;						\
-	}								\
-	!tmp_clen;							\
-})
-
 	/* Search cookie name. */
 	for (chunk = *pos; chunk != end; ++chunk) {
 		if (!(chunk->flags & TFW_STR_NAME))
@@ -933,26 +938,26 @@ tfw_http_search_cookie(const char *cstr, unsigned long clen,
 		if (op == TFW_HTTP_MATCH_O_PREFIX ||
 		    op == TFW_HTTP_MATCH_O_EQ)
 		{
-			if (TFW_STR_EQ_CSTR(end))
+			if (__tfw_str_eq_cstr(cstr, clen, &chunk, end))
 				break;
 			while ((chunk + 1 != end) &&
 			        ((chunk + 1)->flags & TFW_STR_NAME))
 				++chunk;
 		}
 		else if (op == TFW_HTTP_MATCH_O_SUFFIX) {
-			TfwStr *name, t;
-			unsigned int len = 0, name_n = 0;
+			TfwStr *name, *orig;
+			unsigned int len = 0;
 			ssize_t offset;
 
-			for (name = chunk; name != end; ++name, ++name_n) {
+			for (name = chunk; name != end; ++name) {
 				if (!(name->flags & TFW_STR_NAME))
 					break;
 				len += name->len;
 			}
 
 			offset = len - clen;
 			if (!offset) {
-				if (TFW_STR_EQ_CSTR(name))
+				if (__tfw_str_eq_cstr(cstr, clen, &chunk, name))
 					break;
 			} else if (offset > 0) {
 				bool equal;
@@ -961,11 +966,13 @@ tfw_http_search_cookie(const char *cstr, unsigned long clen,
 					offset -= chunk->len;
 					++chunk;
 				}
-				t = *chunk;
+				orig = chunk;
 				chunk->data += offset;
 				chunk->len -= offset;
-				equal =  TFW_STR_EQ_CSTR(name);
-				*chunk = t;
+				equal = __tfw_str_eq_cstr(cstr, clen, &chunk,
+							  name);
+				orig->data -= offset;
+				orig->len += offset;
 				if (equal)
 					break;
 			}
@@ -997,6 +1004,4 @@ tfw_http_search_cookie(const char *cstr, unsigned long clen,
 	}
 	*pos = tfw_str_collect_cmp(chunk, end, val, ";");
 	return 1;
-
-#undef TFW_STR_EQ_CSTR
 }