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…ket-issue, origin/bgp-snmp-socket-issue) (sonic-net#3604)

Author: sudhanshukumar22 <sudhanshu.kumar@broadcom.com>
Date:   Tue Oct 15 02:31:20 2019 -0700

    lib: changes for making snmp socket non-blocking

    Description: The changes have been done to make the snmp socket
    non-blocking before calling snmp_read()
    FRR Pull request: FRRouting/frr#5134

    Problem Description/Summary :
    vtysh hangs on first try to enter after a reboot with BGP dynamic peers

    Expected Behavior :
    VTYSH should not hang.
    When we debug more into bgpd docker by doing gdb on its threads, we find the below thread of bgpd, which is causing the issue.
    Thread 1 (Thread 0x7f1e1ec46d40 (LWP 47)):

    0x00007f1e1d762593 in recvfrom () from /lib/x86_64-linux-gnu/libpthread.so.0
    0x00007f1e1aadd09b in netsnmp_tcpbase_recv () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
    0x00007f1e1aad9617 in netsnmp_transport_recv () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
    0x00007f1e1aab2c07 in _sess_read () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
    0x00007f1e1aab3a29 in snmp_sess_read2 () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
    0x00007f1e1aab3a7b in snmp_read2 () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
    0x00007f1e1aab3acf in snmp_read () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
    0x00007f1e1b44d7ec in agentx_read (t=0x7fffa75f0080) at lib/agentx.c:63
    0x00007f1e1e7d6451 in thread_call (thread=0x7fffa75f0080) at lib/thread.c:1620
    0x00007f1e1e770699 in frr_run (master=0x559396ea60f0) at lib/libfrr.c:1011
    0x0000559395b4d953 in main (argc=5, argv=0x7fffa75f02b8) at bgpd/bgp_main.c:492

    (gdb) bt

    0x00007f830c89d210 in __read_nocancel () from /lib/x86_64-linux-gnu/libpthread.so.0
    0x000056450e1e8238 in vtysh_client_run (vclient=0x56450e4a8b40 <vtysh_client+24768>, line=0x56450e21add0 enable, callback=0x0, cbarg=0x0) at vtysh/vtysh.c:216
    0x000056450e1e8c6b in vtysh_client_run_all (head_client=0x56450e4a8b40 <vtysh_client+24768>, line=0x56450e21add0 enable, continue_on_err=0, callback=0x0, cbarg=0x0) at vtysh/vtysh.c:356
    0x000056450e1e8ddb in vtysh_client_execute (head_client=0x56450e4a8b40 <vtysh_client+24768>, line=0x56450e21add0 enable) at vtysh/vtysh.c:393
    0x000056450e1e9c82 in vtysh_execute_func (line=0x56450e21add0 enable, pager=0) at vtysh/vtysh.c:598
    0x000056450e1e9dee in vtysh_execute_no_pager (line=0x56450e21add0 enable) at vtysh/vtysh.c:619
    0x000056450e1f7d48 in vtysh_read_file (confp=0x56451000a9d0, top_cfg=1) at vtysh/vtysh_config.c:494
    0x000056450e1f7ef2 in vtysh_read_config (config_default_dir=0x56450e4edc20 <frr_config> /etc/frr/frr.conf, top_cfg=1) at vtysh/vtysh_config.c:522
    0x000056450e1e5de4 in vtysh_apply_top_level_config () at vtysh/vtysh_main.c:301
    0x000056450e1e7842 in main (argc=2, argv=0x7ffc81e6f598, env=0x7ffc81e6f5b0) at vtysh/vtysh_main.c:692

    The fix has been taken from the following link.
    https://sourceforge.net/p/net-snmp/patches/1348/

Signed-off-by: Zhenggen Xu <zxu@linkedin.com>

RB=2119458
G=lnos-reviewers
R=pchaudhary,pmao,vapatil,samaity,zxu
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sudhanshukumar22 authored and zhenggen-xu committed May 30, 2020
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85 changes: 85 additions & 0 deletions src/sonic-frr/patch/0006-changes-for-making-snmp-socket-non-blocking.patch
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@@ -0,0 +1,85 @@
From 6d43b90540c6aeda0fff001de93c88e01aacadab Mon Sep 17 00:00:00 2001
From: sudhanshukumar22 <sudhanshu.kumar@broadcom.com>
Date: Tue, 15 Oct 2019 02:11:01 -0700
Subject: [PATCH] lib: changes for making snmp socket non-blocking

Description: The changes have been done to make the snmp socket
non-blocking before calling snmp_read()
FRR Pull request: https://github.com/FRRouting/frr/pull/5134

Problem Description/Summary :
vtysh hangs on first try to enter after a reboot with BGP dynamic peers

Expected Behavior :
VTYSH should not hang.
When we debug more into bgpd docker by doing gdb on its threads, we find the below thread of bgpd, which is causing the issue.
Thread 1 (Thread 0x7f1e1ec46d40 (LWP 47)):

0x00007f1e1d762593 in recvfrom () from /lib/x86_64-linux-gnu/libpthread.so.0
0x00007f1e1aadd09b in netsnmp_tcpbase_recv () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
0x00007f1e1aad9617 in netsnmp_transport_recv () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
0x00007f1e1aab2c07 in _sess_read () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
0x00007f1e1aab3a29 in snmp_sess_read2 () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
0x00007f1e1aab3a7b in snmp_read2 () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
0x00007f1e1aab3acf in snmp_read () from /usr/lib/x86_64-linux-gnu/libnetsnmp.so.30
0x00007f1e1b44d7ec in agentx_read (t=0x7fffa75f0080) at lib/agentx.c:63
0x00007f1e1e7d6451 in thread_call (thread=0x7fffa75f0080) at lib/thread.c:1620
0x00007f1e1e770699 in frr_run (master=0x559396ea60f0) at lib/libfrr.c:1011
0x0000559395b4d953 in main (argc=5, argv=0x7fffa75f02b8) at bgpd/bgp_main.c:492

(gdb) bt

0x00007f830c89d210 in __read_nocancel () from /lib/x86_64-linux-gnu/libpthread.so.0
0x000056450e1e8238 in vtysh_client_run (vclient=0x56450e4a8b40 <vtysh_client+24768>, line=0x56450e21add0 enable, callback=0x0, cbarg=0x0) at vtysh/vtysh.c:216
0x000056450e1e8c6b in vtysh_client_run_all (head_client=0x56450e4a8b40 <vtysh_client+24768>, line=0x56450e21add0 enable, continue_on_err=0, callback=0x0, cbarg=0x0) at vtysh/vtysh.c:356
0x000056450e1e8ddb in vtysh_client_execute (head_client=0x56450e4a8b40 <vtysh_client+24768>, line=0x56450e21add0 enable) at vtysh/vtysh.c:393
0x000056450e1e9c82 in vtysh_execute_func (line=0x56450e21add0 enable, pager=0) at vtysh/vtysh.c:598
0x000056450e1e9dee in vtysh_execute_no_pager (line=0x56450e21add0 enable) at vtysh/vtysh.c:619
0x000056450e1f7d48 in vtysh_read_file (confp=0x56451000a9d0, top_cfg=1) at vtysh/vtysh_config.c:494
0x000056450e1f7ef2 in vtysh_read_config (config_default_dir=0x56450e4edc20 <frr_config> /etc/frr/frr.conf, top_cfg=1) at vtysh/vtysh_config.c:522
0x000056450e1e5de4 in vtysh_apply_top_level_config () at vtysh/vtysh_main.c:301
0x000056450e1e7842 in main (argc=2, argv=0x7ffc81e6f598, env=0x7ffc81e6f5b0) at vtysh/vtysh_main.c:692

The fix has been taken from the following link.
https://sourceforge.net/p/net-snmp/patches/1348/
---
lib/agentx.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/lib/agentx.c b/lib/agentx.c
index 40cac722a..2c6a43d1a 100644
--- a/lib/agentx.c
+++ b/lib/agentx.c
@@ -55,13 +55,29 @@ static int agentx_timeout(struct thread *t)
static int agentx_read(struct thread *t)
{
fd_set fds;
+ int flags;
+ int nonblock = false;
struct listnode *ln = THREAD_ARG(t);
list_delete_node(events, ln);

+ /* fix for non blocking socket */
+ flags = fcntl(THREAD_FD(t), F_GETFL, 0);
+ if (-1 == flags)
+ return -1;
+
+ if (flags & O_NONBLOCK)
+ nonblock = true;
+ else
+ fcntl(THREAD_FD(t), F_SETFL, flags | O_NONBLOCK);
+
FD_ZERO(&fds);
FD_SET(THREAD_FD(t), &fds);
snmp_read(&fds);

+ /* Reset the flag */
+ if (!nonblock)
+ fcntl(THREAD_FD(t), F_SETFL, flags);
+
netsnmp_check_outstanding_agent_requests();
agentx_events_update();
return 0;
--
2.18.0

1 change: 1 addition & 0 deletions src/sonic-frr/patch/series
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@@ -1,2 +1,3 @@
0001-zebra-kernel-level-graceful-restart.patch
0002-bgp-vty-show-sum.patch
0006-changes-for-making-snmp-socket-non-blocking.patch

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