Netlink datagrams can be measured, credentials name their sender
Epiphany's main thread spun at 100% on GLib's network monitor. GLib sizes each netlink datagram with recvmsg(MSG_PEEK|MSG_TRUNC) and no buffer; that answered 0, GLib read 0 bytes, the answer stayed queued and poll() said readable again, forever. recvmsg on netlink now peeks without consuming and with MSG_TRUNC returns what is waiting. A drained netlink socket also no longer reports hangup -- it has no peer, and sock_hup took that for a closed one. SCM_CREDENTIALS under SO_PASSCRED named the process that created the far end, not the one that wrote to it. For a socketpair those differ: WebKit makes the pair, hands one end to a child, and learns the child's pid from the credentials on its first byte. Each end now records its last writer. LDLS: napi_consume_skb frees the skb. r8169 frees every sent frame with it, and as a stub it leaked one per frame until the DMA heap ran out. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
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5 changed files with 120 additions and 2 deletions
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@ -839,6 +839,7 @@ static void *kpi_leds_list[2] = { kpi_leds_list, kpi_leds_list };
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extern int kpi_queue_delayed_work_on(int cpu, void *q, void *dwork, unsigned long delay);
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extern int kpi_cancel_work_sync(void *work);
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extern void kpi_kfree_skb(void *skb);
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const struct kpi_sym kpi_base_table[] = {
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// printing, formatted
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@ -945,6 +946,10 @@ const struct kpi_sym kpi_base_table[] = {
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{ "crc32_le", (void *)kpi_crc32_le },
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{ "get_random_bytes", (void *)kpi_get_random_bytes },
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{ "__skb_pad", (void *)kpi_skb_pad },
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// r8169 frees every transmitted skb this way; a stub leaked one per frame
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// until the DMA heap ran out. The budget argument changes only which cache
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// Linux returns it to.
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{ "napi_consume_skb", (void *)kpi_kfree_skb },
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// data
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{ "link_mode_params", (void *)kpi_link_mode_params },
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