Messages in this thread Patch in this message | | | Date | Thu, 18 Nov 2021 08:36:55 -0700 | Subject | Re: [PATCH v2 net-next 0/2] net: snmp: tracepoint support for snmp | From | David Ahern <> |
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On 11/18/21 5:48 AM, menglong8.dong@gmail.com wrote: > From: Menglong Dong <imagedong@tencent.com> > > snmp is the network package statistics module in kernel, and it is > useful in network issue diagnosis, such as packet drop. > > However, it is hard to get the detail information about the packet. > For example, we can know that there is something wrong with the > checksum of udp packet though 'InCsumErrors' of UDP protocol in > /proc/net/snmp, but we can't figure out the ip and port of the packet > that this error is happening on. > > Add tracepoint for snmp. Therefor, users can use some tools (such as > eBPF) to get the information of the exceptional packet. > > In the first patch, the frame of snmp-tracepoint is created. And in > the second patch, tracepoint for udp-snmp is introduced. >
there is already good infrastructure around kfree_skb - e.g., drop watch monitor. Why not extend that in a way that other drop points can benefit over time?
e.g., something like this (uncompiled and not tested; and to which Steven is going to suggest strings for the reason):
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 0bd6520329f6..e66e634acad0 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1075,8 +1075,13 @@ static inline bool skb_unref(struct sk_buff *skb) return true; }
+enum skb_drop_reason { + SKB_DROP_REASON_NOT_SPECIFIED, + SKB_DROP_REASON_CSUM, +} void skb_release_head_state(struct sk_buff *skb); void kfree_skb(struct sk_buff *skb); +void kfree_skb_with_reason(struct sk_buff *skb, enum skb_drop_reason); void kfree_skb_list(struct sk_buff *segs); void skb_dump(const char *level, const struct sk_buff *skb, bool full_pkt); void skb_tx_error(struct sk_buff *skb); diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h index 9e92f22eb086..2a2d263f9d46 100644 --- a/include/trace/events/skb.h +++ b/include/trace/events/skb.h @@ -14,7 +14,7 @@ */ TRACE_EVENT(kfree_skb,
- TP_PROTO(struct sk_buff *skb, void *location), + TP_PROTO(struct sk_buff *skb, void *location, enum skb_drop_reason reason),
TP_ARGS(skb, location),
@@ -22,16 +22,18 @@ TRACE_EVENT(kfree_skb, __field( void *, skbaddr ) __field( void *, location ) __field( unsigned short, protocol ) + __field( unsigned int, reason ) ),
TP_fast_assign( __entry->skbaddr = skb; __entry->location = location; __entry->protocol = ntohs(skb->protocol); + __entry->reason = reason; ),
- TP_printk("skbaddr=%p protocol=%u location=%p", - __entry->skbaddr, __entry->protocol, __entry->location) + TP_printk("skbaddr=%p protocol=%u location=%p reason %u", + __entry->skbaddr, __entry->protocol, __entry->location, __entry->reason) );
TRACE_EVENT(consume_skb, diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 67a9188d8a49..388059bda3d1 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -770,11 +770,29 @@ void kfree_skb(struct sk_buff *skb) if (!skb_unref(skb)) return;
- trace_kfree_skb(skb, __builtin_return_address(0)); + trace_kfree_skb(skb, __builtin_return_address(0), SKB_DROP_REASON_NOT_SPECIFIED); __kfree_skb(skb); } EXPORT_SYMBOL(kfree_skb);
+/** + * kfree_skb_with_reason - free an sk_buff + * @skb: buffer to free + * @reason: enum describing why the skb is dropped + * + * Drop a reference to the buffer and free it if the usage count has + * hit zero. + */ +void kfree_skb_with_reason(struct sk_buff *skb, enum skb_drop_reason reason); +{ + if (!skb_unref(skb)) + return; + + trace_kfree_skb(skb, __builtin_return_address(0), reason); + __kfree_skb(skb); +} +EXPORT_SYMBOL(kfree_skb_with_reason); + void kfree_skb_list(struct sk_buff *segs) { while (segs) {
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