Merge branch 'reorganize-the-code-of-the-enum-skb_drop_reason'

Menglong Dong says:

====================
reorganize the code of the enum skb_drop_reason

The code of skb_drop_reason is a little wild, let's reorganize them.
Three things and three patches:

1) Move the enum 'skb_drop_reason' and related function to the standalone
   header 'dropreason.h', as Jakub Kicinski suggested, as the skb drop
   reasons are getting more and more.

2) use auto-generation to generate the source file that convert enum
   skb_drop_reason to string.

3) make the comment of skb drop reasons kernel-doc style.

Changes since v3:
3/3: remove some useless comment (Jakub Kicinski)

Changes since v2:
2/3: - add new line in the end of .gitignore
     - fix awk warning by make '\;' to ';', as ';' is not need to be
       escaped
     - export 'drop_reasons' in skbuff.c

Changes since v1:
1/3: move dropreason.h from include/linux/ to include/net/ (Jakub Kicinski)
2/3: generate source file instead of header file for drop reasons string
     array (Jakub Kicinski)
3/3: use inline comment (Jakub Kicinski)
====================

Link: https://lore.kernel.org/r/20220606022436.331005-1-imagedong@tencent.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

include/linux/skbuff.h

@@ -43,6 +43,7 @@
 #include <linux/netfilter/nf_conntrack_common.h>
 #endif
 #include <net/net_debug.h>
+#include <net/dropreason.h>
 
 /**
  * DOC: skb checksums
@@ -337,184 +338,6 @@ struct sk_buff_head {
 
 struct sk_buff;
 
-/* The reason of skb drop, which is used in kfree_skb_reason().
- * en...maybe they should be splited by group?
- *
- * Each item here should also be in 'TRACE_SKB_DROP_REASON', which is
- * used to translate the reason to string.
- */
-enum skb_drop_reason {
-	SKB_NOT_DROPPED_YET = 0,
-	SKB_DROP_REASON_NOT_SPECIFIED,	/* drop reason is not specified */
-	SKB_DROP_REASON_NO_SOCKET,	/* socket not found */
-	SKB_DROP_REASON_PKT_TOO_SMALL,	/* packet size is too small */
-	SKB_DROP_REASON_TCP_CSUM,	/* TCP checksum error */
-	SKB_DROP_REASON_SOCKET_FILTER,	/* dropped by socket filter */
-	SKB_DROP_REASON_UDP_CSUM,	/* UDP checksum error */
-	SKB_DROP_REASON_NETFILTER_DROP,	/* dropped by netfilter */
-	SKB_DROP_REASON_OTHERHOST,	/* packet don't belong to current
-					 * host (interface is in promisc
-					 * mode)
-					 */
-	SKB_DROP_REASON_IP_CSUM,	/* IP checksum error */
-	SKB_DROP_REASON_IP_INHDR,	/* there is something wrong with
-					 * IP header (see
-					 * IPSTATS_MIB_INHDRERRORS)
-					 */
-	SKB_DROP_REASON_IP_RPFILTER,	/* IP rpfilter validate failed.
-					 * see the document for rp_filter
-					 * in ip-sysctl.rst for more
-					 * information
-					 */
-	SKB_DROP_REASON_UNICAST_IN_L2_MULTICAST, /* destination address of L2
-						  * is multicast, but L3 is
-						  * unicast.
-						  */
-	SKB_DROP_REASON_XFRM_POLICY,	/* xfrm policy check failed */
-	SKB_DROP_REASON_IP_NOPROTO,	/* no support for IP protocol */
-	SKB_DROP_REASON_SOCKET_RCVBUFF,	/* socket receive buff is full */
-	SKB_DROP_REASON_PROTO_MEM,	/* proto memory limition, such as
-					 * 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_TCP_RFC7323_PAWS, /* PAWS check, corresponding to
-					   * LINUX_MIB_PAWSESTABREJECTED
-					   */
-	SKB_DROP_REASON_TCP_INVALID_SEQUENCE, /* Not acceptable SEQ field */
-	SKB_DROP_REASON_TCP_RESET,	/* Invalid RST packet */
-	SKB_DROP_REASON_TCP_INVALID_SYN, /* Incoming packet has unexpected SYN flag */
-	SKB_DROP_REASON_TCP_CLOSE,	/* TCP socket in CLOSE state */
-	SKB_DROP_REASON_TCP_FASTOPEN,	/* dropped by FASTOPEN request socket */
-	SKB_DROP_REASON_TCP_OLD_ACK,	/* TCP ACK is old, but in window */
-	SKB_DROP_REASON_TCP_TOO_OLD_ACK, /* TCP ACK is too old */
-	SKB_DROP_REASON_TCP_ACK_UNSENT_DATA, /* TCP ACK for data we haven't sent yet */
-	SKB_DROP_REASON_TCP_OFO_QUEUE_PRUNE, /* pruned from TCP OFO queue */
-	SKB_DROP_REASON_TCP_OFO_DROP,	/* data already in receive queue */
-	SKB_DROP_REASON_IP_OUTNOROUTES,	/* route lookup failed */
-	SKB_DROP_REASON_BPF_CGROUP_EGRESS,	/* dropped by
-						 * BPF_PROG_TYPE_CGROUP_SKB
-						 * eBPF program
-						 */
-	SKB_DROP_REASON_IPV6DISABLED,	/* IPv6 is disabled on the device */
-	SKB_DROP_REASON_NEIGH_CREATEFAIL,	/* failed to create neigh
-						 * entry
-						 */
-	SKB_DROP_REASON_NEIGH_FAILED,	/* neigh entry in failed state */
-	SKB_DROP_REASON_NEIGH_QUEUEFULL,	/* arp_queue for neigh
-						 * entry is full
-						 */
-	SKB_DROP_REASON_NEIGH_DEAD,	/* neigh entry is dead */
-	SKB_DROP_REASON_TC_EGRESS,	/* dropped in TC egress HOOK */
-	SKB_DROP_REASON_QDISC_DROP,	/* dropped by qdisc when packet
-					 * outputting (failed to enqueue to
-					 * current qdisc)
-					 */
-	SKB_DROP_REASON_CPU_BACKLOG,	/* failed to enqueue the skb to
-					 * the per CPU backlog queue. This
-					 * can be caused by backlog queue
-					 * full (see netdev_max_backlog in
-					 * net.rst) or RPS flow limit
-					 */
-	SKB_DROP_REASON_XDP,		/* dropped by XDP in input path */
-	SKB_DROP_REASON_TC_INGRESS,	/* dropped in TC ingress HOOK */
-	SKB_DROP_REASON_UNHANDLED_PROTO,	/* protocol not implemented
-						 * or not supported
-						 */
-	SKB_DROP_REASON_SKB_CSUM,	/* sk_buff checksum computation
-					 * error
-					 */
-	SKB_DROP_REASON_SKB_GSO_SEG,	/* gso segmentation error */
-	SKB_DROP_REASON_SKB_UCOPY_FAULT,	/* failed to copy data from
-						 * user space, e.g., via
-						 * zerocopy_sg_from_iter()
-						 * or skb_orphan_frags_rx()
-						 */
-	SKB_DROP_REASON_DEV_HDR,	/* device driver specific
-					 * header/metadata is invalid
-					 */
-	/* the device is not ready to xmit/recv due to any of its data
-	 * structure that is not up/ready/initialized, e.g., the IFF_UP is
-	 * not set, or driver specific tun->tfiles[txq] is not initialized
-	 */
-	SKB_DROP_REASON_DEV_READY,
-	SKB_DROP_REASON_FULL_RING,	/* ring buffer is full */
-	SKB_DROP_REASON_NOMEM,		/* error due to OOM */
-	SKB_DROP_REASON_HDR_TRUNC,      /* failed to trunc/extract the header
-					 * from networking data, e.g., failed
-					 * to pull the protocol header from
-					 * frags via pskb_may_pull()
-					 */
-	SKB_DROP_REASON_TAP_FILTER,     /* dropped by (ebpf) filter directly
-					 * attached to tun/tap, e.g., via
-					 * TUNSETFILTEREBPF
-					 */
-	SKB_DROP_REASON_TAP_TXFILTER,	/* dropped by tx filter implemented
-					 * at tun/tap, e.g., check_filter()
-					 */
-	SKB_DROP_REASON_ICMP_CSUM,	/* ICMP checksum error */
-	SKB_DROP_REASON_INVALID_PROTO,	/* the packet doesn't follow RFC
-					 * 2211, such as a broadcasts
-					 * ICMP_TIMESTAMP
-					 */
-	SKB_DROP_REASON_IP_INADDRERRORS,	/* host unreachable, corresponding
-						 * to IPSTATS_MIB_INADDRERRORS
-						 */
-	SKB_DROP_REASON_IP_INNOROUTES,	/* network unreachable, corresponding
-					 * to IPSTATS_MIB_INADDRERRORS
-					 */
-	SKB_DROP_REASON_PKT_TOO_BIG,	/* packet size is too big (maybe exceed
-					 * the MTU)
-					 */
-	SKB_DROP_REASON_MAX,
-};
-
-#define SKB_DR_INIT(name, reason)				\
-	enum skb_drop_reason name = SKB_DROP_REASON_##reason
-#define SKB_DR(name)						\
-	SKB_DR_INIT(name, NOT_SPECIFIED)
-#define SKB_DR_SET(name, reason)				\
-	(name = SKB_DROP_REASON_##reason)
-#define SKB_DR_OR(name, reason)					\
-	do {							\
-		if (name == SKB_DROP_REASON_NOT_SPECIFIED ||	\
-		    name == SKB_NOT_DROPPED_YET)		\
-			SKB_DR_SET(name, reason);		\
-	} while (0)
-
 /* To allow 64K frame to be packed as single skb without frag_list we
  * require 64K/PAGE_SIZE pages plus 1 additional page to allow for
  * buffers which do not start on a page boundary.