error: system library:file_ctrl:Broken pipe:../crypto/bio/bss_file.c:326:calling fflush()

[Kathan Vakharia]

Hi team,

We were trying to generate UDP traffic using the openssl rand command over
a DTLS connection in Linux network namespaces.

After generating certificates,
1. we set up the dtls server on the server namespace using the following
command,
    openssl s_server -dtls -key server.key -cert server.crt -accept 4433

2. We use the following command to generate a UDP flow for 5s on the client
namespace,
    timeout 5s bash -c "while true; do openssl rand -hex 1024;done" |
openssl s_client -dtls -connect 10.0.2.2:4433 -cert client.crt -key
client.key

While executing the above, we notice that the DTLS handshake is done
successfully, but the server does not receive application data; instead, we
encounter the following error,


write:errno=90
> 803B1C61FC7E0000:error:80000020:system library:file_ctrl:Broken
> pipe:../crypto/bio/bss_file.c:326:calling fflush()
> 803B1C61FC7E0000:error:10080002:BIO routines:file_ctrl:system
> lib:../crypto/bio/bss_file.c:328:
>

However, the commands work while generating TCP traffic over a TLS
connection.

Our openssl configurations are,
OpenSSL 3.0.2 15 Mar 2022 (Library: OpenSSL 3.0.2 15 Mar 2022)
built on: Mon Feb  6 17:57:17 2023 UTC
platform: debian-amd64
options:  bn(64,64)
compiler: gcc -fPIC -pthread -m64 -Wa,--noexecstack -Wall -Wa,--noexecstack
-g -O2 -ffile-prefix-map=/build/openssl-hnAO60/openssl-3.0.2=. -flto=auto
-ffat-lto-objects -flto=auto -ffat-lto-objects -fstack-protector-strong
-Wformat -Werror=format-security -DOPENSSL_TLS_SECURITY_LEVEL=2
-DOPENSSL_USE_NODELETE -DL_ENDIAN -DOPENSSL_PIC -DOPENSSL_BUILDING_OPENSSL
-DNDEBUG -Wdate-time -D_FORTIFY_SOURCE=2
OPENSSLDIR: "/usr/lib/ssl"
ENGINESDIR: "/usr/lib/x86_64-linux-gnu/engines-3"
MODULESDIR: "/usr/lib/x86_64-linux-gnu/ossl-modules"
Seeding source: os-specific
CPUINFO: OPENSSL_ia32cap=0x7ffaf3ffffebffff:0x405f5ef2bf67eb

Please help us figure out the solution.

Regards,
Kathan Vakharia and Team
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