syscalls/socket: return 0 for unimplemented SOL_SOCKET options in sys_setsockopt

[Rodrigo-Ichaso]

Problem

SOL_SOCKET is defined as 4095 in hermit-abi. This value cannot be represented as u8, so the Ipproto::try_from conversion that follows the existing SOL_SOCKET check always fails and returns EINVAL for every SOL_SOCKET option except SO_REUSEADDR.

This causes Rust std's TCP socket setup to fail on hermit: during connect() and accept(), std internally calls setsockopt with SOL_SOCKET level (e.g. SO_RCVTIMEO, SO_SNDTIMEO, SO_KEEPALIVE) and the resulting EINVAL (os error 22) surfaces to userspace, making plain HTTP connections impossible.

Reproduced while running a Rust HTTP client (ureq 2.x) inside a hermit unikernel on uhyve with virtio-net. Every connect() returned os error 22 before this fix.

Fix

Match on SOL_SOCKET before the Ipproto conversion and return 0 for all options at that level. Unimplemented options are silently treated as no-ops — consistent with Linux behaviour for unsupported socket options on a given socket type.

SO_REUSEADDR continues to work as before (it was already returning 0).

Testing

Verified with a ureq-based HTTP client compiled for x86_64-unknown-hermit making GET/POST requests over virtio-net to a LAN server. Before this fix: every call failed with os error 22. After: connections succeed normally.

[github-actions]

Benchmark Results

Details

Benchmark	Current: d4af8e1	Previous: f83a235	Performance Ratio
startup_benchmark Build Time	77.59 s	77.08 s	1.01 ❗
startup_benchmark File Size	0.73 MB	0.73 MB	1.00 ❗
Startup Time - 1 core	0.74 s (±0.02 s)	0.73 s (±0.02 s)	1.01
Startup Time - 2 cores	0.74 s (±0.02 s)	0.75 s (±0.02 s)	0.98
Startup Time - 4 cores	0.77 s (±0.02 s)	0.76 s (±0.02 s)	1.01
multithreaded_benchmark Build Time	81.00 s	80.66 s	1.00 ❗
multithreaded_benchmark File Size	0.86 MB	0.86 MB	1.00 ❗
Multithreaded Pi Efficiency - 2 Threads	88.04 % (±7.75 %)	89.44 % (±5.91 %)	0.98
Multithreaded Pi Efficiency - 4 Threads	44.07 % (±2.68 %)	44.06 % (±2.65 %)	1.00
Multithreaded Pi Efficiency - 8 Threads	25.44 % (±1.63 %)	25.56 % (±1.89 %)	1.00
micro_benchmarks Build Time	87.76 s	87.20 s	1.01 ❗
micro_benchmarks File Size	0.87 MB	0.87 MB	1.00 ❗
Scheduling time - 1 thread	67.30 ticks (±2.40 ticks)	67.04 ticks (±1.91 ticks)	1.00
Scheduling time - 2 threads	37.13 ticks (±4.20 ticks)	39.33 ticks (±3.42 ticks)	0.94
Micro - Time for syscall (getpid)	3.51 ticks (±0.29 ticks)	3.43 ticks (±0.24 ticks)	1.02
Memcpy speed - (built_in) block size 4096	83487.47 MByte/s (±57579.19 MByte/s)	84527.91 MByte/s (±58322.62 MByte/s)	0.99
Memcpy speed - (built_in) block size 1048576	30962.29 MByte/s (±25147.68 MByte/s)	30845.87 MByte/s (±25037.16 MByte/s)	1.00
Memcpy speed - (built_in) block size 16777216	27389.24 MByte/s (±22674.44 MByte/s)	27492.52 MByte/s (±22708.20 MByte/s)	1.00
Memset speed - (built_in) block size 4096	83353.47 MByte/s (±57488.64 MByte/s)	84666.80 MByte/s (±58421.97 MByte/s)	0.98
Memset speed - (built_in) block size 1048576	31683.59 MByte/s (±25547.75 MByte/s)	31593.14 MByte/s (±25470.12 MByte/s)	1.00
Memset speed - (built_in) block size 16777216	28156.16 MByte/s (±23146.46 MByte/s)	28269.66 MByte/s (±23193.64 MByte/s)	1.00
Memcpy speed - (rust) block size 4096	74461.95 MByte/s (±51937.87 MByte/s)	74722.10 MByte/s (±52209.99 MByte/s)	1.00
Memcpy speed - (rust) block size 1048576	30868.07 MByte/s (±25103.90 MByte/s)	30824.11 MByte/s (±25054.28 MByte/s)	1.00
Memcpy speed - (rust) block size 16777216	27069.18 MByte/s (±22332.84 MByte/s)	27597.67 MByte/s (±22766.03 MByte/s)	0.98
Memset speed - (rust) block size 4096	74666.60 MByte/s (±52073.47 MByte/s)	74865.22 MByte/s (±52302.23 MByte/s)	1.00
Memset speed - (rust) block size 1048576	31610.83 MByte/s (±25521.63 MByte/s)	31565.59 MByte/s (±25484.76 MByte/s)	1.00
Memset speed - (rust) block size 16777216	27833.53 MByte/s (±22810.79 MByte/s)	28374.92 MByte/s (±23250.83 MByte/s)	0.98
alloc_benchmarks Build Time	80.27 s	81.01 s	0.99 ❗
alloc_benchmarks File Size	0.81 MB	0.81 MB	1.00 ❗
Allocations - Allocation success	91.32 %	91.32 %	1
Allocations - Deallocation success	100.00 %	100.00 %	1
Allocations - Pre-fail Allocations	61.46 %	61.46 %	1
Allocations - Average Allocation time	6121.01 Ticks (±134.89 Ticks)	6133.98 Ticks (±129.62 Ticks)	1.00
Allocations - Average Allocation time (no fail)	6760.79 Ticks (±172.70 Ticks)	6784.80 Ticks (±184.79 Ticks)	1.00
Allocations - Average Deallocation time	1265.47 Ticks (±248.24 Ticks)	1292.85 Ticks (±344.36 Ticks)	0.98
mutex_benchmark Build Time	81.92 s	81.90 s	1.00 ❗
mutex_benchmark File Size	0.87 MB	0.87 MB	1.00 ❗
Mutex Stress Test Average Time per Iteration - 1 Threads	12.06 ns (±0.51 ns)	12.08 ns (±0.27 ns)	1.00
Mutex Stress Test Average Time per Iteration - 2 Threads	17.56 ns (±2.75 ns)	17.94 ns (±3.62 ns)	0.98

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