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@@ -1005,6 +1005,32 @@ fetch_from_buf(char *string, size_t string_len, buf_t *buf)
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return (int)buf->datalen;
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}
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+/** True iff the cell command <b>command</b> is one that implies a variable-length
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+ * cell in Tor link protocol <b>linkproto</b>. */
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+static inline int
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+cell_command_is_var_length(uint8_t command, int linkproto)
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+{
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+ /* If linkproto is v2 (2), CELL_VERSIONS is the only variable-length cells work as
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+ * implemented here. If it's 1, there are no variable-length cells. Tor
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+ * does not support other versions right now, and so can't negotiate them.
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+ */
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+ switch (linkproto) {
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+ case 1:
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+ /* Link protocol version 1 has no variable-length cells. */
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+ return 0;
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+ case 2:
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+ /* In link protocol version 2, VERSIONS is the only variable-length cell */
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+ return command == CELL_VERSIONS;
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+ case 0:
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+ case 3:
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+ default:
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+ /* In link protocol version 3 and later, and in version "unknown",
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+ * commands 128 and higher indicate variable-length. VERSIONS is
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+ * grandfathered in. */
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+ return command == CELL_VERSIONS || command >= 128;
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+ }
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+}
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+
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/** Check <b>buf</b> for a variable-length cell according to the rules of link
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* protocol version <b>linkproto</b>. If one is found, pull it off the buffer
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* and assign a newly allocated var_cell_t to *<b>out</b>, and return 1.
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@@ -1019,12 +1045,6 @@ fetch_var_cell_from_buf(buf_t *buf, var_cell_t **out, int linkproto)
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var_cell_t *result;
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uint8_t command;
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uint16_t length;
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- /* If linkproto is unknown (0) or v2 (2), variable-length cells work as
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- * implemented here. If it's 1, there are no variable-length cells. Tor
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- * does not support other versions right now, and so can't negotiate them.
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- */
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- if (linkproto == 1)
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- return 0;
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check();
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*out = NULL;
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if (buf->datalen < VAR_CELL_HEADER_SIZE)
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@@ -1032,7 +1052,7 @@ fetch_var_cell_from_buf(buf_t *buf, var_cell_t **out, int linkproto)
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peek_from_buf(hdr, sizeof(hdr), buf);
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command = get_uint8(hdr+2);
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- if (!(CELL_COMMAND_IS_VAR_LENGTH(command)))
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+ if (!(cell_command_is_var_length(command, linkproto)))
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return 0;
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length = ntohs(get_uint16(hdr+3));
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@@ -1101,8 +1121,6 @@ fetch_var_cell_from_evbuffer(struct evbuffer *buf, var_cell_t **out,
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uint16_t cell_length;
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var_cell_t *cell;
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int result = 0;
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- if (linkproto == 1)
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- return 0;
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*out = NULL;
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buf_len = evbuffer_get_length(buf);
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@@ -1113,7 +1131,7 @@ fetch_var_cell_from_evbuffer(struct evbuffer *buf, var_cell_t **out,
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tor_assert(n >= VAR_CELL_HEADER_SIZE);
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command = get_uint8(hdr+2);
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- if (!(CELL_COMMAND_IS_VAR_LENGTH(command))) {
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+ if (!(cell_command_is_var_length(command, linkproto))) {
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goto done;
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}
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