#define TCP_MAX_WND_SCALE 14 /* See RFC 1323 */
#define TCP_OPTS_ALIGN 4
#define TCP_OPTS_MAX_SACK_BLOCKS 3
+
+/* Modulo arithmetic for TCP sequence numbers */
+#define seq_lt(_s1, _s2) ((i32)((_s1)-(_s2)) < 0)
+#define seq_leq(_s1, _s2) ((i32)((_s1)-(_s2)) <= 0)
+#define seq_gt(_s1, _s2) ((i32)((_s1)-(_s2)) > 0)
+#define seq_geq(_s1, _s2) ((i32)((_s1)-(_s2)) >= 0)
+#define seq_max(_s1, _s2) (seq_gt((_s1), (_s2)) ? (_s1) : (_s2))
+
+/* Modulo arithmetic for timestamps */
+#define timestamp_lt(_t1, _t2) ((i32)((_t1)-(_t2)) < 0)
+#define timestamp_leq(_t1, _t2) ((i32)((_t1)-(_t2)) <= 0)
+
+/**
+ * Parse TCP header options.
+ *
+ * @param th TCP header
+ * @param to TCP options data structure to be populated
+ * @param is_syn set if packet is syn
+ * @return -1 if parsing failed
+ */
+always_inline int
+tcp_options_parse (tcp_header_t * th, tcp_options_t * to, u8 is_syn)
+{
+ const u8 *data;
+ u8 opt_len, opts_len, kind;
+ int j;
+ sack_block_t b;
+
+ opts_len = (tcp_doff (th) << 2) - sizeof (tcp_header_t);
+ data = (const u8 *) (th + 1);
+
+ /* Zero out all flags but those set in SYN */
+ to->flags &= (TCP_OPTS_FLAG_SACK_PERMITTED | TCP_OPTS_FLAG_WSCALE
+ | TCP_OPTS_FLAG_TSTAMP | TCP_OPTS_FLAG_MSS);
+
+ for (; opts_len > 0; opts_len -= opt_len, data += opt_len)
+ {
+ kind = data[0];
+
+ /* Get options length */
+ if (kind == TCP_OPTION_EOL)
+ break;
+ else if (kind == TCP_OPTION_NOOP)
+ {
+ opt_len = 1;
+ continue;
+ }
+ else
+ {
+ /* broken options */
+ if (opts_len < 2)
+ return -1;
+ opt_len = data[1];
+
+ /* weird option length */
+ if (opt_len < 2 || opt_len > opts_len)
+ return -1;
+ }
+
+ /* Parse options */
+ switch (kind)
+ {
+ case TCP_OPTION_MSS:
+ if (!is_syn)
+ break;
+ if ((opt_len == TCP_OPTION_LEN_MSS) && tcp_syn (th))
+ {
+ to->flags |= TCP_OPTS_FLAG_MSS;
+ to->mss = clib_net_to_host_u16 (*(u16 *) (data + 2));
+ }
+ break;
+ case TCP_OPTION_WINDOW_SCALE:
+ if (!is_syn)
+ break;
+ if ((opt_len == TCP_OPTION_LEN_WINDOW_SCALE) && tcp_syn (th))
+ {
+ to->flags |= TCP_OPTS_FLAG_WSCALE;
+ to->wscale = data[2];
+ if (to->wscale > TCP_MAX_WND_SCALE)
+ to->wscale = TCP_MAX_WND_SCALE;
+ }
+ break;
+ case TCP_OPTION_TIMESTAMP:
+ if (is_syn)
+ to->flags |= TCP_OPTS_FLAG_TSTAMP;
+ if ((to->flags & TCP_OPTS_FLAG_TSTAMP)
+ && opt_len == TCP_OPTION_LEN_TIMESTAMP)
+ {
+ to->tsval = clib_net_to_host_u32 (*(u32 *) (data + 2));
+ to->tsecr = clib_net_to_host_u32 (*(u32 *) (data + 6));
+ }
+ break;
+ case TCP_OPTION_SACK_PERMITTED:
+ if (!is_syn)
+ break;
+ if (opt_len == TCP_OPTION_LEN_SACK_PERMITTED && tcp_syn (th))
+ to->flags |= TCP_OPTS_FLAG_SACK_PERMITTED;
+ break;
+ case TCP_OPTION_SACK_BLOCK:
+ /* If SACK permitted was not advertised or a SYN, break */
+ if ((to->flags & TCP_OPTS_FLAG_SACK_PERMITTED) == 0 || tcp_syn (th))
+ break;
+
+ /* If too short or not correctly formatted, break */
+ if (opt_len < 10 || ((opt_len - 2) % TCP_OPTION_LEN_SACK_BLOCK))
+ break;
+
+ to->flags |= TCP_OPTS_FLAG_SACK;
+ to->n_sack_blocks = (opt_len - 2) / TCP_OPTION_LEN_SACK_BLOCK;
+ vec_reset_length (to->sacks);
+ for (j = 0; j < to->n_sack_blocks; j++)
+ {
+ b.start = clib_net_to_host_u32 (*(u32 *) (data + 2 + 8 * j));
+ b.end = clib_net_to_host_u32 (*(u32 *) (data + 6 + 8 * j));
+ vec_add1 (to->sacks, b);
+ }
+ break;
+ default:
+ /* Nothing to see here */
+ continue;
+ }
+ }
+ return 0;
+}
+
+/**
+ * Write TCP options to segment.
+ *
+ * @param data buffer where to write the options
+ * @param opts options to write
+ * @return length of options written
+ */
+always_inline u32
+tcp_options_write (u8 * data, tcp_options_t * opts)
+{
+ u32 opts_len = 0;
+ u32 buf, seq_len = 4;
+
+ if (tcp_opts_mss (opts))
+ {
+ *data++ = TCP_OPTION_MSS;
+ *data++ = TCP_OPTION_LEN_MSS;
+ buf = clib_host_to_net_u16 (opts->mss);
+ clib_memcpy_fast (data, &buf, sizeof (opts->mss));
+ data += sizeof (opts->mss);
+ opts_len += TCP_OPTION_LEN_MSS;
+ }
+
+ if (tcp_opts_wscale (opts))
+ {
+ *data++ = TCP_OPTION_WINDOW_SCALE;
+ *data++ = TCP_OPTION_LEN_WINDOW_SCALE;
+ *data++ = opts->wscale;
+ opts_len += TCP_OPTION_LEN_WINDOW_SCALE;
+ }
+
+ if (tcp_opts_sack_permitted (opts))
+ {
+ *data++ = TCP_OPTION_SACK_PERMITTED;
+ *data++ = TCP_OPTION_LEN_SACK_PERMITTED;
+ opts_len += TCP_OPTION_LEN_SACK_PERMITTED;
+ }
+
+ if (tcp_opts_tstamp (opts))
+ {
+ *data++ = TCP_OPTION_TIMESTAMP;
+ *data++ = TCP_OPTION_LEN_TIMESTAMP;
+ buf = clib_host_to_net_u32 (opts->tsval);
+ clib_memcpy_fast (data, &buf, sizeof (opts->tsval));
+ data += sizeof (opts->tsval);
+ buf = clib_host_to_net_u32 (opts->tsecr);
+ clib_memcpy_fast (data, &buf, sizeof (opts->tsecr));
+ data += sizeof (opts->tsecr);
+ opts_len += TCP_OPTION_LEN_TIMESTAMP;
+ }
+
+ if (tcp_opts_sack (opts))
+ {
+ int i;
+
+ if (opts->n_sack_blocks != 0)
+ {
+ *data++ = TCP_OPTION_SACK_BLOCK;
+ *data++ = 2 + opts->n_sack_blocks * TCP_OPTION_LEN_SACK_BLOCK;
+ for (i = 0; i < opts->n_sack_blocks; i++)
+ {
+ buf = clib_host_to_net_u32 (opts->sacks[i].start);
+ clib_memcpy_fast (data, &buf, seq_len);
+ data += seq_len;
+ buf = clib_host_to_net_u32 (opts->sacks[i].end);
+ clib_memcpy_fast (data, &buf, seq_len);
+ data += seq_len;
+ }
+ opts_len += 2 + opts->n_sack_blocks * TCP_OPTION_LEN_SACK_BLOCK;
+ }
+ }
+
+ /* Terminate TCP options */
+ if (opts_len % 4)
+ {
+ *data++ = TCP_OPTION_EOL;
+ opts_len += TCP_OPTION_LEN_EOL;
+ }
+
+ /* Pad with zeroes to a u32 boundary */
+ while (opts_len % 4)
+ {
+ *data++ = TCP_OPTION_NOOP;
+ opts_len += TCP_OPTION_LEN_NOOP;
+ }
+ return opts_len;
+}
+
#endif /* included_tcp_packet_h */
/*
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