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authorDavid S. Miller <davem@davemloft.net>2022-02-20 13:55:31 +0000
committerDavid S. Miller <davem@davemloft.net>2022-02-20 13:55:31 +0000
commitadfb62dbda49d66eba6340324547ff89b09a66eb (patch)
tree1fa0f39a846de21459ed1cb7cdada1ffea216917 /include/linux
parent48c77bdf729a91fa7f65765d3f60f01e0ac320c5 (diff)
parentd25e481be0c519d1a458b14191dc8c2a8bb3e24a (diff)
Merge branch 'tcp_drop_reason'
Menglong Dong says: ==================== net: add skb drop reasons to TCP packet receive In the commit c504e5c2f964 ("net: skb: introduce kfree_skb_reason()"), we added the support of reporting the reasons of skb drops to kfree_skb tracepoint. And in this series patches, reasons for skb drops are added to TCP layer (both TCPv4 and TCPv6 are considered). Following functions are processed: tcp_v4_rcv() tcp_v6_rcv() tcp_v4_inbound_md5_hash() tcp_v6_inbound_md5_hash() tcp_add_backlog() tcp_v4_do_rcv() tcp_v6_do_rcv() tcp_rcv_established() tcp_data_queue() tcp_data_queue_ofo() The functions we handled are mostly for packet ingress, as skb drops hardly happens in the egress path of TCP layer. However, it's a little complex for TCP state processing, as I find that it's hard to report skb drop reasons to where it is freed. For example, when skb is dropped in tcp_rcv_state_process(), the reason can be caused by the call of tcp_v4_conn_request(), and it's hard to return a drop reason from tcp_v4_conn_request(). So such cases are skipped for this moment. Following new drop reasons are introduced (what they mean can be see in the document for them): /* SKB_DROP_REASON_TCP_MD5* corresponding to LINUX_MIB_TCPMD5* */ SKB_DROP_REASON_TCP_MD5NOTFOUND SKB_DROP_REASON_TCP_MD5UNEXPECTED SKB_DROP_REASON_TCP_MD5FAILURE SKB_DROP_REASON_SOCKET_BACKLOG SKB_DROP_REASON_TCP_FLAGS SKB_DROP_REASON_TCP_ZEROWINDOW SKB_DROP_REASON_TCP_OLD_DATA SKB_DROP_REASON_TCP_OVERWINDOW /* corresponding to LINUX_MIB_TCPOFOMERGE */ SKB_DROP_REASON_TCP_OFOMERGE Here is a example to get TCP packet drop reasons from ftrace: $ echo 1 > /sys/kernel/debug/tracing/events/skb/kfree_skb/enable $ cat /sys/kernel/debug/tracing/trace $ <idle>-0 [036] ..s1. 647.428165: kfree_skb: skbaddr=000000004d037db6 protocol=2048 location=0000000074cd1243 reason: NO_SOCKET $ <idle>-0 [020] ..s2. 639.676674: kfree_skb: skbaddr=00000000bcbfa42d protocol=2048 location=00000000bfe89d35 reason: PROTO_MEM From the reason 'PROTO_MEM' we can know that the skb is dropped because the memory configured in net.ipv4.tcp_mem is up to the limition. Changes since v2: - remove the 'inline' of tcp_drop() in the 1th patch, as Jakub suggested Changes since v1: - enrich the document for this series patches in the cover letter, as Eric suggested - fix compile warning report by Jakub in the 6th patch - let NO_SOCKET trump the XFRM failure in the 2th and 3th patches ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/skbuff.h34
1 files changed, 34 insertions, 0 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a5adbf6b51e8..a3e90efe6586 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -346,6 +346,40 @@ enum skb_drop_reason {
* udp packet drop out of
* udp_memory_allocated.
*/
+ SKB_DROP_REASON_TCP_MD5NOTFOUND, /* no MD5 hash and one
+ * expected, corresponding
+ * to LINUX_MIB_TCPMD5NOTFOUND
+ */
+ SKB_DROP_REASON_TCP_MD5UNEXPECTED, /* MD5 hash and we're not
+ * expecting one, corresponding
+ * to LINUX_MIB_TCPMD5UNEXPECTED
+ */
+ SKB_DROP_REASON_TCP_MD5FAILURE, /* MD5 hash and its wrong,
+ * corresponding to
+ * LINUX_MIB_TCPMD5FAILURE
+ */
+ SKB_DROP_REASON_SOCKET_BACKLOG, /* failed to add skb to socket
+ * backlog (see
+ * LINUX_MIB_TCPBACKLOGDROP)
+ */
+ SKB_DROP_REASON_TCP_FLAGS, /* TCP flags invalid */
+ SKB_DROP_REASON_TCP_ZEROWINDOW, /* TCP receive window size is zero,
+ * see LINUX_MIB_TCPZEROWINDOWDROP
+ */
+ SKB_DROP_REASON_TCP_OLD_DATA, /* the TCP data reveived is already
+ * received before (spurious retrans
+ * may happened), see
+ * LINUX_MIB_DELAYEDACKLOST
+ */
+ SKB_DROP_REASON_TCP_OVERWINDOW, /* the TCP data is out of window,
+ * the seq of the first byte exceed
+ * the right edges of receive
+ * window
+ */
+ SKB_DROP_REASON_TCP_OFOMERGE, /* the data of skb is already in
+ * the ofo queue, corresponding to
+ * LINUX_MIB_TCPOFOMERGE
+ */
SKB_DROP_REASON_MAX,
};