Per-socket TCP internals

Show rtt/cwnd/retrans per socket for 443; pinpoint slow/lossy peers

ss -tip state established '( dport = :443 )'
tool
iproute212 commands
tags
iproute2ssperformancenetworkdebug

More iproute2 commands

  • Kill sockets by filter
    ss -K dst <ip> dport = :8080

    Forcibly close matching sockets (kernel>=4.9); needs CONFIG_INET_DIAG_DESTROY

  • Add secondary IP
    ip addr add 10.0.0.5/24 dev <name> && ip addr show dev <name>

    Assign a secondary IP/prefix live; note: not persisted across reboot

  • Set interface MTU
    ip link set dev <name> mtu 9000 && ip link set dev <name> up

    Set jumbo MTU and bring link up; note: path MTU must match end-to-end

  • JSON addr to jq
    ip -j a | jq -r '.[] | select(.operstate=="UP") | .ifname + " " + (.addr_info[]?.local // "-")'

    Machine-readable interface dump; list UP links with their local IPs

  • Which route is chosen
    ip route get <ip>

    Show the exact route, src IP and oif the kernel picks for a destination

all 12 iproute2 commands