Hi, perhaps you can tell me if I'm doing something wrong.
I'm playing with BPF_MAP_TYPE_SOCKMAP map with trivial BPF_SK_SKB_STREAM_PARSER and BPF_SK_SKB_STREAM_VERDICT ebpf programs to do basic TCP echo server. The code: https://gist.github.com/majek/a09bcbeb8ab548cde6c18c930895c3f2#file-sockmap-echo-kern-c-L17 >>> SEC("prog_parser") int _prog_parser(struct __sk_buff *skb) { (void)skb; return 4096; } SEC("prog_verdict") int _prog_verdict(struct __sk_buff *skb) { uint32_t idx = 0; return bpf_sk_redirect_map(skb, &sock_map, idx, 0); } <<< Notice the unconditional 4096 in prog_parser. To reproduce: git clone git://gist.github.com/a09bcbeb8ab548cde6c18c930895c3f2.git cd a09bcbeb8ab548cde6c18c930895c3f2/ make sudo ./sockmap-echo [+] Accepting on 0.0.0.0:4321 Then on the remote node: $ yes | nc -q 1 -vvvv 10.133.8.66 4321 |wc -l What is expected: not crashing, returning the same amount of data as piped into nc. What do I get: couple of things, but let's start with simplest: kernel panic related to GRO/GSO. The code works okay (doesn't crash) until I play with GRO/GSO on the sockmap-echo node: $ sudo ethtool -K int0 gro off gso off Cannot get device udp-fragmentation-offload settings: Operation not supported Cannot get device udp-fragmentation-offload settings: Operation not supported I'm running this on "sfc" network card, with vlans: 03:00.0 Ethernet controller: Solarflare Communications SFC9120 (rev 01) $ sudo modinfo sfc filename: /lib/modules/4.19.13-cloudflare-2019.1.4/kernel/drivers/net/ethernet/sfc/sfc.ko version: 4.14.0.1014 license: GPL description: Solarflare network driver author: Solarflare Communications and Michael Brown <mbr...@fensystems.co.uk> srcversion: 89349D4C6CB39AA17FE7FE3 ... depends: mdio name: sfc vermagic: 4.19.13-cloudflare-2019.1.4 SMP mod_unload After disabling GRO/GSO I see: [ 1378.455127] BUG: stack guard page was hit at 0000000045d41b2c (stack is 000000001743f701..000000002e3b4c89) [ 1378.472896] kernel stack overflow (double-fault): 0000 [#1] SMP PTI [ 1378.487149] CPU: 21 PID: 53397 Comm: kworker/21:1 Tainted: G O 4.19.13-cloudflare-2019.1.4 #2019.1.4 [ 1378.505777] Hardware name: Quanta Computer Inc QuantaPlex T41S-2U/S2S-MB, BIOS S2S_3B10.03 06/21/2018 [ 1378.523280] Workqueue: events smap_tx_work [ 1378.535633] RIP: 0010:__put_page+0x1b/0x30 [ 1378.547935] Code: 0f 1f 44 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 8b 07 f6 c4 80 74 02 eb b1 48 8b 47 08 a8 01 75 f6 53 48 89 fb <e8> 90 fd ff ff 48 89 df 5b e9 17 6c ff ff 0f 1f 80 00 00 00 00 0f [ 1378.583257] RSP: 0018:ffff8def490e4000 EFLAGS: 00010246 [ 1378.596498] RAX: dead000000000100 RBX: ffffe1753f4a7640 RCX: ffffe1753e9bb688 [ 1378.611647] RDX: dead0000000000ff RSI: ffffe175403aa688 RDI: ffffe1753f4a7640 [ 1378.611648] RBP: ffff8bf27274f9c0 R08: ffff8c00fffdea00 R09: ffffffffb3eb4800 [ 1378.611648] R10: ffff8c005dc90100 R11: 0000000000000001 R12: ffff8c005dc91600 [ 1378.611649] R13: 0000000000002238 R14: ffff8c00a9024ec0 R15: 0ffff8c00bfb6480 [ 1378.611651] FS: 0000000000000000(0000) GS:ffff8c00bfb40000(0000) knlGS:0000000000000000 [ 1378.611651] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1378.611652] CR2: ffff8def490e3ff8 CR3: 0000001dcf00a002 CR4: 00000000001606e0 [ 1378.611653] Call Trace: [ 1378.611662] skb_release_data+0x88/0x140 [ 1378.611664] ? skb_release_data+0xa5/0x140 [ 1378.611666] kfree_skb+0x32/0xa0 [ 1378.611668] skb_release_data+0xa5/0x140 [ 1378.611670] ? skb_release_data+0xa5/0x140 [ 1378.611674] kfree_skb+0x32/0xa0 [ 1378.795283] skb_release_data+0xa5/0x140 [ 1378.795285] ? skb_release_data+0xa5/0x140 [ 1378.795287] kfree_skb+0x32/0xa0 [ 1378.795288] skb_release_data+0xa5/0x140 [ 1378.795290] ? skb_release_data+0xa5/0x140 [ 1378.795292] kfree_skb+0x32/0xa0 [ 1378.795294] skb_release_data+0xa5/0x140 [ 1378.795295] ? skb_release_data+0xa5/0x140 [ 1378.795297] kfree_skb+0x32/0xa0 ... [ 1385.038439] smap_tx_work+0x236/0x2b0 [ 1385.046811] process_one_work+0x1fa/0x3f0 [ 1385.055539] ? rescuer_thread+0x330/0x330 [ 1385.064199] worker_thread+0x2d/0x3d0 [ 1385.072532] ? rescuer_thread+0x330/0x330 [ 1385.081204] kthread+0x113/0x130 [ 1385.089095] ? kthread_create_worker_on_cpu+0x70/0x70 [ 1385.098901] ret_from_fork+0x35/0x40 [ 1385.107197] Modules linked in: ... [ 1385.249536] ---[ end trace 2750106f41eb6d8e ]--- $ cat /proc/version Linux version 4.19.13-cloudflare-2019.1.4 (builder@cf-tc-agent) (gcc version 8.2.0 (GCC)) #2019.1.4 SMP Wed Jan 9 11:04:31 UTC 2019 I'm having more problems with this sockmap-echo code, but at this moment this is the simplest thing to reproduce. Marek
