xnu-517.9.5.tar.gz

[apple/xnu.git] / bsd / netinet / tcp.h

diff --git a/bsd/netinet/tcp.h b/bsd/netinet/tcp.h
index 39efb3d79c6a822054596343a5eb0fc92cba38f1..30479bd881b9eb45bf003b35a67147e1ce7bae83 100644 (file)
--- a/bsd/netinet/tcp.h
+++ b/bsd/netinet/tcp.h
@@ -123,12 +123,23 @@ struct tcphdr {
 
 /*
  * Default maximum segment size for TCP.
- * With an IP MSS of 576, this is 536,
+ * With an IP MTU of 576, this is 536,
  * but 512 is probably more convenient.
  * This should be defined as MIN(512, IP_MSS - sizeof (struct tcpiphdr)).
  */
 #define        TCP_MSS 512
 
+/*
+ * TCP_MINMSS is defined to be 216 which is fine for the smallest
+ * link MTU (256 bytes, SLIP interface) in the Internet.
+ * However it is very unlikely to come across such low MTU interfaces
+ * these days (anno dato 2004).
+ * Probably it can be set to 512 without ill effects. But we play safe.
+ * See tcp_subr.c tcp_minmss SYSCTL declaration for more comments.
+ * Setting this to "0" disables the minmss check.
+ */
+#define        TCP_MINMSS 216
+
 /*
  * Default maximum segment size for TCP6.
  * With an IP6 MSS of 1280, this is 1220,
@@ -155,5 +166,6 @@ struct tcphdr {
 #define        TCP_MAXSEG      0x02    /* set maximum segment size */
 #define TCP_NOPUSH     0x04    /* don't push last block of write */
 #define TCP_NOOPT      0x08    /* don't use TCP options */
+#define TCP_KEEPALIVE  0x10    /* idle time used when SO_KEEPALIVE is enabled */
 
 #endif