Re-comment sbcompress() to explain what it is it does; it took me

quite a bit of reading to figure it out, and I want to avoid figuring
it out again.

Convert an if (foo) else printf("this is almost a panic") into a
KASSERT.

MFC after:	3 days

1 files changed, 20 insertions, 7 deletions

diff --git a/sys/kern/uipc_sockbuf.c b/sys/kern/uipc_sockbuf.c
index e979251..16fa1f8 100644
--- a/sys/kern/uipc_sockbuf.c
+++ b/sys/kern/uipc_sockbuf.c
@@ -1027,9 +1027,24 @@ sbappendcontrol(sb, m0, control)
 }
 
 /*
- * Compress mbuf chain m into the socket
- * buffer sb following mbuf n.  If n
- * is null, the buffer is presumed empty.
+ * Append the data in mbuf chain (m) into the socket buffer sb following mbuf
+ * (n).  If (n) is NULL, the buffer is presumed empty.
+ *
+ * When the data is compressed, mbufs in the chain may be handled in one of
+ * three ways:
+ *
+ * (1) The mbuf may simply be dropped, if it contributes nothing (no data, no
+ *     record boundary, and no change in data type).
+ *
+ * (2) The mbuf may be coalesced -- i.e., data in the mbuf may be copied into
+ *     an mbuf already in the socket buffer.  This can occur if an
+ *     appropriate mbuf exists, there is room, and no merging of data types
+ *     will occur.
+ *
+ * (3) The mbuf may be appended to the end of the existing mbuf chain.
+ *
+ * If any of the new mbufs is marked as M_EOR, mark the last mbuf appended as
+ * end-of-record.
  */
 void
 sbcompress(sb, m, n)
@@ -1080,10 +1095,8 @@ sbcompress(sb, m, n)
 		n->m_next = 0;
 	}
 	if (eor) {
-		if (n)
-			n->m_flags |= eor;
-		else
-			printf("semi-panic: sbcompress\n");
+		KASSERT(n != NULL, ("sbcompress: eor && n == NULL"));
+		n->m_flags |= eor;
 	}
 	SBLASTMBUFCHK(sb);
 }