From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:30:08
From: Nikolay Aleksandrov <redacted>
Hi,
This set tries to help with an old ask that we've had for some time
which is to print nexthop information while monitoring or dumping routes.
The core problem is that people cannot follow nexthop changes while
monitoring route changes, by the time they check the nexthop it could be
deleted or updated to something else. In order to help them out I've
added a nexthop cache which is populated (only used if -d / show_details
is specified) while decoding routes and kept up to date while monitoring.
The nexthop information is printed on its own line starting with the
"nh_info" attribute and its embedded inside it if printing JSON. To
cache the nexthop entries I parse them into structures, in order to
reuse most of the code the print helpers have been altered so they rely
on prepared structures. Nexthops are now always parsed into a structure,
even if they won't be cached, that structure is later used to print the
nexthop and destroyed if not going to be cached. New nexthops (not found
in the cache) are retrieved from the kernel using a private netlink
socket so they don't disrupt an ongoing dump, similar to how interfaces
are retrieved and cached.
I have tested the set with the kernel forwarding selftests and also by
stressing it with nexthop create/update/delete in loops while monitoring.
Comments are very welcome as usual. :)
Patch breakdown:
Patches 1-2: update current route helpers to take parsed arguments so we
can directly pass them from the nh_entry structure later
Patch 3: adds the new nh_entry structure and a helper to parse nhmsg
into it
Patch 4: adds resilient nexthop group structure and a parser for it
Patch 5: converts current nexthop print code to always parse the
nhmsg into nh_entry structure and use it for printing
Patch 6: factors out ipnh_get's rtnl talk part and allows to use a
different rt handle for the communication
Patch 7: adds nexthop cache and helpers to manage it, it uses the
new __ipnh_get to retrieve nexthops
Patch 8: factors out nh_entry printing into a separate helper called
__print_nexthop_entry
Patch 9: adds a new helper print_cache_nexthop_id that prints nexthop
information from its id, if the nexthop is not found in the
cache it fetches it
Patch 10: the new print_cache_nexthop_id helper is used when printing
routes with show_details (-d) to output detailed nexthop
information, the format after nh_info is the same as
ip nexthop show
Patch 11: changes print_nexthop into print_cache_nexthop which always
outputs the nexthop information and can also update the cache
(based on process_cache argument), it's used to keep the
cache up to date while monitoring
Example outputs (monitor):
[NEXTHOP]id 101 via 169.254.2.22 dev veth2 scope link proto unspec
[NEXTHOP]id 102 via 169.254.3.23 dev veth4 scope link proto unspec
[NEXTHOP]id 103 group 101/102 type resilient buckets 512 idle_timer 0 unbalanced_timer 0 unbalanced_time 0 scope global proto unspec
[ROUTE]unicast 192.0.2.0/24 nhid 203 table 4 proto boot scope global
nh_info id 203 group 201/202 type resilient buckets 512 idle_timer 0 unbalanced_timer 0 unbalanced_time 0 scope global proto unspec
nexthop via 169.254.2.12 dev veth3 weight 1
nexthop via 169.254.3.13 dev veth5 weight 1
[NEXTHOP]id 204 via fe80:2::12 dev veth3 scope link proto unspec
[NEXTHOP]id 205 via fe80:3::13 dev veth5 scope link proto unspec
[NEXTHOP]id 206 group 204/205 type resilient buckets 512 idle_timer 0 unbalanced_timer 0 unbalanced_time 0 scope global proto unspec
[ROUTE]unicast 2001:db8:1::/64 nhid 206 table 4 proto boot scope global metric 1024 pref medium
nh_info id 206 group 204/205 type resilient buckets 512 idle_timer 0 unbalanced_timer 0 unbalanced_time 0 scope global proto unspec
nexthop via fe80:2::12 dev veth3 weight 1
nexthop via fe80:3::13 dev veth5 weight 1
[NEXTHOP]id 2 encap mpls 200/300 via 10.1.1.1 dev ens20 scope link proto unspec onlink
[ROUTE]unicast 2.3.4.10 nhid 2 table main proto boot scope global
nh_info id 2 encap mpls 200/300 via 10.1.1.1 dev ens20 scope link proto unspec onlink
JSON:
{
"type": "unicast",
"dst": "198.51.100.0/24",
"nhid": 103,
"table": "3",
"protocol": "boot",
"scope": "global",
"flags": [ ],
"nh_info": {
"id": 103,
"group": [ {
"id": 101,
"weight": 11
},{
"id": 102,
"weight": 45
} ],
"type": "resilient",
"resilient_args": {
"buckets": 512,
"idle_timer": 0,
"unbalanced_timer": 0,
"unbalanced_time": 0
},
"scope": "global",
"protocol": "unspec",
"flags": [ ]
},
"nexthops": [ {
"gateway": "169.254.2.22",
"dev": "veth2",
"weight": 11,
"flags": [ ]
},{
"gateway": "169.254.3.23",
"dev": "veth4",
"weight": 45,
"flags": [ ]
} ]
}
Thank you,
Nik
Nikolay Aleksandrov (11):
ip: print_rta_if takes ifindex as device argument instead of attribute
ip: export print_rta_gateway version which outputs prepared gateway
string
ip: nexthop: add nh struct and a helper to parse nhmsg into it
ip: nexthop: parse resilient nexthop group attribute into structure
ip: nexthop: always parse attributes for printing
ip: nexthop: pull ipnh_get_id rtnl talk into a helper
ip: nexthop: add cache helpers
ip: nexthop: factor out entry printing
ip: nexthop: add a helper which retrieves and prints cached nh entry
ip: route: print and cache detailed nexthop information when requested
ip: nexthop: add print_cache_nexthop which prints and manages the nh
cache
ip/ip_common.h | 4 +-
ip/ipmonitor.c | 3 +-
ip/ipnexthop.c | 455 +++++++++++++++++++++++++++++++++++++++----------
ip/iproute.c | 32 ++--
ip/nh_common.h | 53 ++++++
5 files changed, 446 insertions(+), 101 deletions(-)
create mode 100644 ip/nh_common.h
--
2.31.1
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:29:45
From: Nikolay Aleksandrov <redacted>
Add a structure which describes a nexthop with all of its properties and
a helper which parses a nhmsg into it. Note the LWT attribute is copied
because there are too many different types with their own structures,
having to follow them all for changes would be overkill. It's much better
to copy the attribtue and pass it for decoding to the lwt code which is
already well maintained.
Signed-off-by: Nikolay Aleksandrov <redacted>
---
ip/ipnexthop.c | 97 +++++++++++++++++++++++++++++++++++++++++++++++++-
ip/nh_common.h | 33 +++++++++++++++++
2 files changed, 129 insertions(+), 1 deletion(-)
create mode 100644 ip/nh_common.h
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:29:47
From: Nikolay Aleksandrov <redacted>
Add a structure which describes resilient nexthop groups and parse such
attributes into it.
Signed-off-by: Nikolay Aleksandrov <redacted>
---
ip/ipnexthop.c | 32 ++++++++++++++++++++++++++++++++
ip/nh_common.h | 10 ++++++++++
2 files changed, 42 insertions(+)
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:29:48
From: Nikolay Aleksandrov <redacted>
We need print_rta_if() to take ifindex directly so later we can use it
with cached converted nexthop objects.
Signed-off-by: Nikolay Aleksandrov <redacted>
---
ip/ip_common.h | 2 +-
ip/ipnexthop.c | 2 +-
ip/iproute.c | 12 ++++++------
3 files changed, 8 insertions(+), 8 deletions(-)
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:29:55
From: Nikolay Aleksandrov <redacted>
Export a new __print_rta_gateway that takes a prepared gateway string to
print which is also used by print_rta_gateway for consistent format.
Signed-off-by: Nikolay Aleksandrov <redacted>
---
ip/ip_common.h | 1 +
ip/iproute.c | 15 ++++++++++-----
2 files changed, 11 insertions(+), 5 deletions(-)
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:29:58
From: Nikolay Aleksandrov <redacted>
Add a new helper print_cache_nexthop replacing print_nexthop which can
update the nexthop cache if the process_cache argument is true. It is
used when monitoring netlink messages to keep the nexthop cache up to
date with nexthop changes happening. For the old callers and anyone
who's just dumping nexthops its _nocache version is used which is a
wrapper for print_cache_nexthop.
Signed-off-by: Nikolay Aleksandrov <redacted>
---
ip/ip_common.h | 1 -
ip/ipmonitor.c | 3 ++-
ip/ipnexthop.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++----
ip/nh_common.h | 1 +
4 files changed, 52 insertions(+), 6 deletions(-)
@@ -602,7 +602,43 @@ static void __print_nexthop_entry(FILE *fp, const char *jsobj,close_json_object();}-intprint_nexthop(structnlmsghdr*n,void*arg)+/* update, add or delete a nexthop entry based on nlmsghdr */+staticintipnh_cache_process_nlmsg(conststructnlmsghdr*n,+structnh_entry*new_nhe)+{+structnh_entry*nhe;++nhe=ipnh_cache_get(new_nhe->nh_id);+switch(n->nlmsg_type){+caseRTM_DELNEXTHOP:+if(nhe)+ipnh_cache_del(nhe);+ipnh_destroy_entry(new_nhe);+break;+caseRTM_NEWNEXTHOP:+if(!nhe){+nhe=malloc(sizeof(*nhe));+if(!nhe){+ipnh_destroy_entry(new_nhe);+return-1;+}+}else{+/* this allows us to save 1 allocation on updates by+*reusingtheoldnhentry,butweneedtocleanupits+*internalstorage+*/+ipnh_cache_unlink_entry(nhe);+ipnh_destroy_entry(nhe);+}+memcpy(nhe,new_nhe,sizeof(*nhe));+ipnh_cache_link_entry(nhe);+break;+}++return0;+}++intprint_cache_nexthop(structnlmsghdr*n,void*arg,boolprocess_cache){structnhmsg*nhm=NLMSG_DATA(n);FILE*fp=(FILE*)arg;
@@ -635,11 +671,20 @@ int print_nexthop(struct nlmsghdr *n, void *arg)__print_nexthop_entry(fp,NULL,&nhe,n->nlmsg_type==RTM_DELNEXTHOP);print_string(PRINT_FP,NULL,"%s","\n");fflush(fp);-ipnh_destroy_entry(&nhe);++if(process_cache)+ipnh_cache_process_nlmsg(n,&nhe);+else+ipnh_destroy_entry(&nhe);return0;}+staticintprint_nexthop_nocache(structnlmsghdr*n,void*arg)+{+returnprint_cache_nexthop(n,arg,false);+}+voidprint_cache_nexthop_id(FILE*fp,constchar*fp_prefix,constchar*jsobj,__u32nh_id){
@@ -967,7 +1012,7 @@ static int ipnh_get_id(__u32 id)new_json_obj(json);-if(print_nexthop(answer,(void*)stdout)<0){+if(print_nexthop_nocache(answer,(void*)stdout)<0){free(answer);return-1;}
@@ -1052,7 +1097,7 @@ static int ipnh_list_flush(int argc, char **argv, int action)new_json_obj(json);-if(rtnl_dump_filter(&rth,print_nexthop,stdout)<0){+if(rtnl_dump_filter(&rth,print_nexthop_nocache,stdout)<0){fprintf(stderr,"Dump terminated\n");return-2;}
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:30:01
From: Nikolay Aleksandrov <redacted>
Always parse nexthop group attributes into structure for printing. Nexthop
print helpers take structures and print them accordingly.
Signed-off-by: Nikolay Aleksandrov <redacted>
---
ip/ipnexthop.c | 117 +++++++++++++++++++++----------------------------
1 file changed, 49 insertions(+), 68 deletions(-)
@@ -261,15 +255,14 @@ static const char *nh_group_type_name(__u16 type)}}-staticvoidprint_nh_group_type(FILE*fp,conststructrtattr*grp_type_attr)+staticvoidprint_nh_group_type(__u16nh_grp_type){-__u16type=rta_getattr_u16(grp_type_attr);--if(type==NEXTHOP_GRP_TYPE_MPATH)+if(nh_grp_type==NEXTHOP_GRP_TYPE_MPATH)/* Do not print type in order not to break existing output. */return;-print_string(PRINT_ANY,"type","type %s ",nh_group_type_name(type));+print_string(PRINT_ANY,"type","type %s ",+nh_group_type_name(nh_grp_type));}staticvoidparse_nh_res_group_rta(conststructrtattr*res_grp_attr,
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:30:04
From: Nikolay Aleksandrov <redacted>
Pull ipnh_get_id's rtnl talk portion into a separate helper which will
be reused later to retrieve nexthops for caching.
Signed-off-by: Nikolay Aleksandrov <redacted>
---
ip/ipnexthop.c | 33 ++++++++++++++++++++-------------
1 file changed, 20 insertions(+), 13 deletions(-)
@@ -820,21 +839,9 @@ static int ipnh_modify(int cmd, unsigned int flags, int argc, char **argv)staticintipnh_get_id(__u32id){-struct{-structnlmsghdrn;-structnhmsgnhm;-charbuf[1024];-}req={-.n.nlmsg_len=NLMSG_LENGTH(sizeof(structnhmsg)),-.n.nlmsg_flags=NLM_F_REQUEST,-.n.nlmsg_type=RTM_GETNEXTHOP,-.nhm.nh_family=preferred_family,-};structnlmsghdr*answer;-addattr32(&req.n,sizeof(req),NHA_ID,id);--if(rtnl_talk(&rth,&req.n,&answer)<0)+if(__ipnh_get_id(&rth,id,&answer)<0)return-2;new_json_obj(json);
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:30:07
From: Nikolay Aleksandrov <redacted>
Add a helper which looks for a nexthop in the cache and if not found
reads the entry from the kernel and caches it. Finally the entry is
printed.
Signed-off-by: Nikolay Aleksandrov <redacted>
---
ip/ipnexthop.c | 16 ++++++++++++++++
ip/nh_common.h | 3 +++
2 files changed, 19 insertions(+)
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:30:09
From: Nikolay Aleksandrov <redacted>
Add a static nexthop cache in a hash with 1024 buckets and helpers to
manage it (link, unlink, find, add nexthop, del nexthop). Adding new
nexthops is done by creating a new rtnl handle and using it to retrieve
the nexthop so the helper is safe to use while already reading a
response (i.e. using the global rth).
Signed-off-by: Nikolay Aleksandrov <redacted>
---
ip/ipnexthop.c | 112 +++++++++++++++++++++++++++++++++++++++++++++----
ip/nh_common.h | 6 +++
2 files changed, 111 insertions(+), 7 deletions(-)
@@ -347,6 +349,41 @@ static void ipnh_destroy_entry(struct nh_entry *nhe)free(nhe->nh_groups);}+staticstructhlist_head*ipnh_cache_head(__u32nh_id)+{+nh_id^=nh_id>>20;+nh_id^=nh_id>>10;++return&nh_cache[nh_id%NH_CACHE_SIZE];+}++staticvoidipnh_cache_link_entry(structnh_entry*nhe)+{+structhlist_head*head=ipnh_cache_head(nhe->nh_id);++hlist_add_head(&nhe->nh_hash,head);+}++staticvoidipnh_cache_unlink_entry(structnh_entry*nhe)+{+hlist_del(&nhe->nh_hash);+}++staticstructnh_entry*ipnh_cache_get(__u32nh_id)+{+structhlist_head*head=ipnh_cache_head(nh_id);+structnh_entry*nhe;+structhlist_node*n;++hlist_for_each(n,head){+nhe=container_of(n,structnh_entry,nh_hash);+if(nhe->nh_id==nh_id)+returnnhe;+}++returnNULL;+}+/* parse nhmsg into nexthop entry struct which must be destroyed by*ipnh_destroy_entywhenit'snotneededanymore*/
@@ -372,7 +409,7 @@ static int ipnh_parse_nhmsg(FILE *fp, const struct nhmsg *nhm, int len,if(RTA_PAYLOAD(tb[NHA_GATEWAY])>sizeof(nhe->nh_gateway)){fprintf(fp,"<nexthop id %u invalid gateway length %lu>\n",nhe->nh_id,RTA_PAYLOAD(tb[NHA_GATEWAY]));-err=EINVAL;+err=-EINVAL;gotoout_err;}nhe->nh_gateway_len=RTA_PAYLOAD(tb[NHA_GATEWAY]);
@@ -383,7 +420,7 @@ static int ipnh_parse_nhmsg(FILE *fp, const struct nhmsg *nhm, int len,if(tb[NHA_ENCAP]){nhe->nh_encap=malloc(RTA_LENGTH(RTA_PAYLOAD(tb[NHA_ENCAP])));if(!nhe->nh_encap){-err=ENOMEM;+err=-ENOMEM;gotoout_err;}memcpy(nhe->nh_encap,tb[NHA_ENCAP],
@@ -396,13 +433,13 @@ static int ipnh_parse_nhmsg(FILE *fp, const struct nhmsg *nhm, int len,if(!__valid_nh_group_attr(tb[NHA_GROUP])){fprintf(fp,"<nexthop id %u invalid nexthop group>",nhe->nh_id);-err=EINVAL;+err=-EINVAL;gotoout_err;}nhe->nh_groups=malloc(RTA_PAYLOAD(tb[NHA_GROUP]));if(!nhe->nh_groups){-err=ENOMEM;+err=-ENOMEM;gotoout_err;}nhe->nh_groups_cnt=RTA_PAYLOAD(tb[NHA_GROUP])/
@@ -450,6 +487,67 @@ static int __ipnh_get_id(struct rtnl_handle *rthp, __u32 nh_id,returnrtnl_talk(rthp,&req.n,answer);}+staticint__ipnh_cache_parse_nlmsg(conststructnlmsghdr*n,+structnh_entry*nhe)+{+interr,len;++len=n->nlmsg_len-NLMSG_SPACE(sizeof(structnhmsg));+if(len<0){+fprintf(stderr,"BUG: wrong nlmsg len %d\n",len);+return-EINVAL;+}++err=ipnh_parse_nhmsg(stderr,NLMSG_DATA(n),len,nhe);+if(err){+fprintf(stderr,"Error parsing nexthop: %s\n",strerror(-err));+returnerr;+}++return0;+}++staticstructnh_entry*ipnh_cache_add(__u32nh_id)+{+structrtnl_handlecache_rth={.fd=-1};+structnlmsghdr*answer=NULL;+structnh_entry*nhe=NULL;++if(rtnl_open(&cache_rth,0)<0)+gotoout;++if(__ipnh_get_id(&cache_rth,nh_id,&answer)<0)+gotoout;++nhe=malloc(sizeof(*nhe));+if(!nhe)+gotoout;++if(__ipnh_cache_parse_nlmsg(answer,nhe))+gotoout_free_nhe;++ipnh_cache_link_entry(nhe);++out:+if(answer)+free(answer);+rtnl_close(&cache_rth);++returnnhe;++out_free_nhe:+free(nhe);+nhe=NULL;+gotoout;+}++staticvoidipnh_cache_del(structnh_entry*nhe)+{+ipnh_cache_unlink_entry(nhe);+ipnh_destroy_entry(nhe);+free(nhe);+}+intprint_nexthop(structnlmsghdr*n,void*arg){structnhmsg*nhm=NLMSG_DATA(n);
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:30:16
From: Nikolay Aleksandrov <redacted>
Factor out nexthop entry printing into a separate function.
Signed-off-by: Nikolay Aleksandrov <redacted>
---
ip/ipnexthop.c | 103 ++++++++++++++++++++++++++-----------------------
1 file changed, 55 insertions(+), 48 deletions(-)
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-29 15:30:21
From: Nikolay Aleksandrov <redacted>
If -d (show_details) is used when printing/monitoring routes then print
detailed nexthop information in the field "nh_info". The nexthop is also
cached for future searches.
Output looks like:
unicast 198.51.100.0/24 nhid 103 table 3 proto boot scope global
nh_info id 103 group 101/102 type resilient buckets 512 idle_timer 0 unbalanced_timer 0 unbalanced_time 0 scope global proto unspec
nexthop via 169.254.2.22 dev veth2 weight 1
nexthop via 169.254.3.23 dev veth4 weight 1
The nh_info field has the same format as ip -d nexthop show would've had
for the same nexthop id.
For completeness the JSON version looks like:
{
"type": "unicast",
"dst": "198.51.100.0/24",
"nhid": 103,
"table": "3",
"protocol": "boot",
"scope": "global",
"flags": [ ],
"nh_info": {
"id": 103,
"group": [ {
"id": 101
},{
"id": 102
} ],
"type": "resilient",
"resilient_args": {
"buckets": 512,
"idle_timer": 0,
"unbalanced_timer": 0,
"unbalanced_time": 0
},
"scope": "global",
"protocol": "unspec",
"flags": [ ]
},
"nexthops": [ {
"gateway": "169.254.2.22",
"dev": "veth2",
"weight": 1,
"flags": [ ]
},{
"gateway": "169.254.3.23",
"dev": "veth4",
"weight": 1,
"flags": [ ]
} ]
}
Signed-off-by: Nikolay Aleksandrov <redacted>
---
ip/iproute.c | 5 +++++
1 file changed, 5 insertions(+)
From: David Ahern <hidden> Date: 2021-09-30 03:33:53
On 9/29/21 9:28 AM, Nikolay Aleksandrov wrote:
quoted hunk
@@ -328,6 +336,93 @@ static void print_nh_res_bucket(FILE *fp, const struct rtattr *res_bucket_attr) close_json_object(); }+static void ipnh_destroy_entry(struct nh_entry *nhe)+{+ if (nhe->nh_encap)+ free(nhe->nh_encap);+ if (nhe->nh_groups)+ free(nhe->nh_groups);+}++/* parse nhmsg into nexthop entry struct which must be destroyed by+ * ipnh_destroy_enty when it's not needed anymore+ */
I'd rather not have 2 functions interpreting the attributes. You should
be able to get print_nexthop to use the parse function and then print
using the nh_entry.
From: David Ahern <hidden> Date: 2021-09-30 03:42:13
On 9/29/21 9:28 AM, Nikolay Aleksandrov wrote:
From: Nikolay Aleksandrov <redacted>
Hi,
This set tries to help with an old ask that we've had for some time
which is to print nexthop information while monitoring or dumping routes.
The core problem is that people cannot follow nexthop changes while
monitoring route changes, by the time they check the nexthop it could be
deleted or updated to something else. In order to help them out I've
added a nexthop cache which is populated (only used if -d / show_details
is specified) while decoding routes and kept up to date while monitoring.
The nexthop information is printed on its own line starting with the
"nh_info" attribute and its embedded inside it if printing JSON. To
cache the nexthop entries I parse them into structures, in order to
reuse most of the code the print helpers have been altered so they rely
on prepared structures. Nexthops are now always parsed into a structure,
even if they won't be cached, that structure is later used to print the
nexthop and destroyed if not going to be cached. New nexthops (not found
in the cache) are retrieved from the kernel using a private netlink
socket so they don't disrupt an ongoing dump, similar to how interfaces
are retrieved and cached.
I have tested the set with the kernel forwarding selftests and also by
stressing it with nexthop create/update/delete in loops while monitoring.
Comments are very welcome as usual. :)
overall it looks fine and not surprised a cache is needed.
Big comment is to re-order the patches - do all of the refactoring first
to get the code where you need it and then add what is needed for the cache.
so you are doing that but in reverse order. Re-order the patches such
that existing code is refactored with the parse functions first.
I added the parse functions first without any functional changes and converted
the existing printing code to use them in this patch after that. I don't mind
doing the conversion after each parse function is added, too.
From: Nikolay Aleksandrov <razor@blackwall.org> Date: 2021-09-30 07:17:08
On 30/09/2021 06:42, David Ahern wrote:
On 9/29/21 9:28 AM, Nikolay Aleksandrov wrote:
quoted
From: Nikolay Aleksandrov <redacted>
Hi,
This set tries to help with an old ask that we've had for some time
which is to print nexthop information while monitoring or dumping routes.
The core problem is that people cannot follow nexthop changes while
monitoring route changes, by the time they check the nexthop it could be
deleted or updated to something else. In order to help them out I've
added a nexthop cache which is populated (only used if -d / show_details
is specified) while decoding routes and kept up to date while monitoring.
The nexthop information is printed on its own line starting with the
"nh_info" attribute and its embedded inside it if printing JSON. To
cache the nexthop entries I parse them into structures, in order to
reuse most of the code the print helpers have been altered so they rely
on prepared structures. Nexthops are now always parsed into a structure,
even if they won't be cached, that structure is later used to print the
nexthop and destroyed if not going to be cached. New nexthops (not found
in the cache) are retrieved from the kernel using a private netlink
socket so they don't disrupt an ongoing dump, similar to how interfaces
are retrieved and cached.
I have tested the set with the kernel forwarding selftests and also by
stressing it with nexthop create/update/delete in loops while monitoring.
Comments are very welcome as usual. :)
overall it looks fine and not surprised a cache is needed.
Big comment is to re-order the patches - do all of the refactoring first
to get the code where you need it and then add what is needed for the cache.
Thanks for the comments, apart from pairing the add parse/use parse functions
in the first few patches only patch 08 seems out of place, although it's there
because it was first needed in patch 09, I don't mind pulling it back.
All other patches after 06 are adding the new cache and print functions and
using them in iproute/ipmonitor, there is no refactoring done in those, so I
plan to keep those as they are.
Cheers,
Nik