Trace network syscalls

Capture all network-related syscalls

strace -e trace=network,socket curl https://example.com 2>&1 | grep -v '^---'
tool
strace13 commands
tags
stracelinuxdebugnetwork

More strace commands

  • Syscall count summary
    strace -c -f -S time -p <pid>

    Aggregate syscall counts/time across forks, sorted by time; pinpoints the costly call

  • Decode fds with timing
    strace -yy -T -tt -e trace=%file -p <pid>

    Show paths/sockets behind fds plus per-call duration and timestamps for file ops

  • Stack trace per syscall
    strace -k -e trace=openat -f -p <pid>

    Print user stack on each openat to find which code path opens a file; needs debug symbols

  • Syscall fault injection
    strace -f -e inject=openat:error=ENOENT:when=3 -p <pid>

    Force the 3rd openat to fail with ENOENT to test error handling; chaos testing without code

  • Trace signals delivered
    strace -f -e signal=all -e trace=none -p <pid>

    Show only signals (SIGTERM/SIGCHLD) and skip syscalls; debug mysterious kills. note: ltrace for libcalls

all 13 strace commands