__socket_cached_read opvector的 len 非法，导致req_len 0，导致返回0 认为对端关闭socket 反复重启链接

[feizai131]

Description of problem:
以下栈 增加的校验core req_len ==0 core
#1 0x00007fa08df34e65 in abort () from /lib64/libc.so.6
#2 0x00007fa08df34d39 in __assert_fail_base.cold.0 () from /lib64/libc.so.6
#3 0x00007fa08df59e86 in __assert_fail () from /lib64/libc.so.6
#4 0x00007f9fa7cded85 in __socket_cached_read (this=0x7f9f68005990, opvector=0x7f9f68005f40, opcount=1) at socket.c:407
#5 0x00007f9fa7cdf3d3 in __socket_rwv (this=0x7f9f68005990, vector=0x7f9f68005f40, count=1, pending_vector=0x7f9f68005fc0, pending_count=0x7f9f68005fc8,
bytes=0x7f9fa723a038, write=0) at socket.c:554
#6 0x00007f9fa7cdf79a in __socket_readv (this=0x7f9f68005990, vector=0x7f9f68005f40, count=1, pending_vector=0x7f9f68005fc0, pending_count=0x7f9f68005fc8,
bytes=0x7f9fa723a038) at socket.c:641
#7 0x00007f9fa7ce2680 in __socket_read_vectored_request (this=0x7f9fa7ce2680 <__socket_read_vectored_request+3522>, vector_sizer=0x7f9fa723a190)
at socket.c:1333
#8 0x00007f9fa7ce3959 in __socket_read_request (this=0x7f9f68005990) at socket.c:1574
#9 0x00007f9fa7ce6719 in __socket_read_frag (this=0x7f9f68005990) at socket.c:2135
#10 0x00007f9fa7ce7b97 in __socket_proto_state_machine (this=0x7f9f68005990, pollin=0x7f9fa723a410) at socket.c:2523
#11 0x00007f9fa7ce8041 in socket_proto_state_machine (this=0x7f9f68005990, pollin=0x7f9fa723a410) at socket.c:2630
#12 0x00007f9fa7ce82eb in socket_event_poll_in_worker (data=0x193f01) at socket.c:2679
#13 0x00007f9fa7ce8b59 in socket_event_handler (fd=38, idx=6, gen=1, data=0x7f9f68005990, poll_in=1, poll_out=0, poll_err=0) at socket.c:2847
#14 0x00007fa08f93934d in event_dispatch_epoll_handler (event_pool=0x8595b0, event=0x7f9fa723a544) at event-epoll.c:523
#15 0x00007fa08f939624 in event_dispatch_epoll_worker (data=0x8a62a0) at event-epoll.c:592
#16 0x00007fa08e7e31ca in start_thread () from /lib64/libpthread.so.0
#17 0x00007fa08df4c8d3 in clone () from /lib64/libc.so.6
(gdb) p opvector
No symbol "opvector" in current context.
(gdb) f 4
#4 0x00007f9fa7cded85 in __socket_cached_read (this=0x7f9f68005990, opvector=0x7f9f68005f40, opcount=1) at socket.c:407
Download failed: Function not implemented. Continuing without source file /data/cpf/2.0.0/hifs-sdk/rpc/rpc-transport/socket/src/socket.c.
407 socket.c: No such file or directory.
(gdb) p opvector
$1 = (struct iovec *) 0x7f9f68005f40
(gdb) p opvector[0]
$2 = {iov_base = 0x7f9f68005f32, iov_len = 21474836480}

The exact command to reproduce the issue:
if (in->ra_served < in->ra_read) {
ret = iov_load(opvector, opcount, &in->ra_buf[in->ra_served],
min(req_len, (in->ra_read - in->ra_served)));

    in->ra_served += ret;
    /* Do not read uncached and cached in the same call */
    goto out;
}由于eq_len 0，导致返回ret 0  此时并不是关闭socket了

The full output of the command that failed:

Expected results:

Mandatory info:
- The output of the gluster volume info command:

- The output of the gluster volume status command:

- The output of the gluster volume heal command:

**- Provide logs present on following locations of client and server nodes -
/var/log/glusterfs/

**- Is there any crash ? Provide the backtrace and coredump

#define __socket_proto_update_pending(priv)
do {
uint32_t remaining;
struct gf_sock_incoming_frag* frag;
frag = &priv->incoming.frag;
if (frag->pending_vector->iov_len == 0) {
remaining = (RPC_FRAGSIZE(priv->incoming.fraghdr) - frag->bytes_read);

frag->pending_vector->iov_len = (remaining > frag->remaining_size) ? frag->remaining_size : remaining;

frag->remaining_size -= frag->pending_vector->iov_len;
、*********priv->incoming.pending_vector = frag->pending_vector; ********
}
} while (0)

priv->incoming.pending_vector ！= frag->pending_vector；

Additional info:

- The operating system / glusterfs version:

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