zhhyu7 commented on code in PR #20627:
URL: https://github.com/apache/nuttx/pull/20627#discussion_r4259566067
##########
net/tcp/tcp_input.c:
##########
@@ -1570,38 +1573,104 @@ static void tcp_input(FAR struct net_driver_s *dev,
uint8_t domain,
if ((tcp->flags & TCP_URG) != 0)
{
- dev->d_urglen = (tcp->urgp[0] << 8) | tcp->urgp[1];
- if (dev->d_urglen > dev->d_len)
+ uint16_t urgp = (tcp->urgp[0] << 8) | tcp->urgp[1];
+
+ /* BSD/Linux default semantics (tcp_stdurg=0):
+ * The urgent pointer points ONE BYTE PAST the urgent byte.
+ * The single urgent byte is at payload[urgp - 1].
+ *
+ * If urgp is within the current segment (1 <= urgp <= d_len):
+ * - Extract the single urgent byte into conn->urgreadahead.
+ * - Compact the remaining payload in place.
+ * - Advance rcvseq by 1 for the urgent byte.
+ *
+ * If urgp > d_len:
+ * - The urgent byte is located in a future segment not yet
+ * received; keep current payload intact in normal stream.
+ *
+ * If urgp == 0:
+ * - Invalid urgent offset; keep payload intact in normal stream.
+ */
+
+#ifdef CONFIG_NET_SOCKOPTS
+ if (urgp >= 1 && urgp <= dev->d_len &&
+ !_SO_GETOPT(conn->sconn.s_options, _SO_OOBINLINE))
+#else
+ if (urgp >= 1 && urgp <= dev->d_len)
+#endif
{
- /* There is more urgent data in the next segment to come. */
+ FAR struct iob_s *urg_iob;
+ uint8_t urg_byte;
+
+ urg_byte = dev->d_appdata[urgp - 1];
+
+ /* BSD/Linux policy: Keep at most one urgent byte.
+ * If an unread urgent byte is already buffered,
+ * overwrite it.
+ */
+
+ if (conn->urgreadahead != NULL)
+ {
+ FAR struct iob_s *uiob = conn->urgreadahead;
+
+ uiob->io_data[uiob->io_offset] = urg_byte;
+ uiob->io_len = 1;
+ uiob->io_pktlen = 1;
+ }
+ else
+ {
+ /* Allocate IOB for the urgent byte */
+
+ urg_iob = iob_tryalloc(true);
+ if (urg_iob == NULL)
+ {
+ /* Memory allocation failed: do not advance
+ * sequence number and do not acknowledge this
+ * data. Drop segment so peer will retransmit.
+ */
+
+ nerr("ERROR: Failed to allocate urgent IOB\n");
+ goto drop;
+ }
+
+ if (iob_trycopyin(urg_iob, &urg_byte, 1, 0, true) < 0)
Review Comment:
At this point the ACK and window update of the segment have already been
processed, but ```goto drop``` skips the ```TCP_ACKDATA``` callback for it.
Only one urgent byte is ever buffered, so a uint8_t plus a state flag in
tcp_conn_s is enough. That removes the allocation, this failure path, and the
1-byte IOB per connection.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
