Port map_txq_config_base_setup from C to Rust

The previous C function was pretty simple, it'd been left as C
for fast porting. It's now a safe (other than the syscall,
which is properly wrapped) Rust function.

src/rust/lqos_sys/src/bpf/wrapper.c

@@ -246,70 +246,3 @@ int tc_attach_ingress(int ifindex, bool verbose, struct lqos_kern *obj)
 out:
 	return err;
 }
-
-/*******************************/
-
-static inline unsigned int bpf_num_possible_cpus(void)
-{
-	static const char *fcpu = "/sys/devices/system/cpu/possible";
-	unsigned int start, end, possible_cpus = 0;
-	char buff[128];
-	FILE *fp;
-	int n;
-
-	fp = fopen(fcpu, "r");
-	if (!fp) {
-		printf("Failed to open %s: '%s'!\n", fcpu, strerror(errno));
-		exit(1);
-	}
-
-	while (fgets(buff, sizeof(buff), fp)) {
-		n = sscanf(buff, "%u-%u", &start, &end);
-		if (n == 0) {
-			printf("Failed to retrieve # possible CPUs!\n");
-			exit(1);
-		} else if (n == 1) {
-			end = start;
-		}
-		possible_cpus = start == 0 ? end + 1 : 0;
-		break;
-	}
-	fclose(fp);
-
-	return possible_cpus;
-}
-
-struct txq_config {
-	/* lookup key: __u32 cpu; */
-	__u16 queue_mapping;
-	__u16 htb_major;
-};
-
-bool map_txq_config_base_setup(int map_fd) {
-	unsigned int possible_cpus = bpf_num_possible_cpus();
-	struct txq_config txq_cfg;
-	__u32 cpu;
-	int err;
-
-	if (map_fd < 0) {
-		fprintf(stderr, "ERR: (bad map_fd:%d) "
-			"cannot proceed without access to txq_config map\n",
-			map_fd);
-		return false;
-	}
-
-	for (cpu = 0; cpu < possible_cpus; cpu++) {
-		txq_cfg.queue_mapping = cpu + 1;
-		txq_cfg.htb_major     = cpu + 1;
-
-		err = bpf_map_update_elem(map_fd, &cpu, &txq_cfg, 0);
-		if (err) {
-			fprintf(stderr,
-				"ERR: %s() updating cpu-key:%d err(%d):%s\n",
-				__func__, cpu, errno, strerror(errno));
-			return false;
-		}
-	}
-
-	return true;
-}

src/rust/lqos_sys/src/bpf/wrapper.h

@@ -8,5 +8,4 @@ extern int tc_detach_egress(int ifindex, bool verbose, bool flush_hook, const ch
 extern int tc_attach_ingress(int ifindex, bool verbose, struct lqos_kern *obj);
 extern int tc_detach_ingress(int ifindex, bool verbose, bool flush_hook, const char * ifname);
 extern __u64 max_tracker_ips();
-extern bool map_txq_config_base_setup(int map_fd);
 extern void do_not_print();

src/rust/lqos_sys/src/cpu_map.rs

@@ -2,8 +2,7 @@ use anyhow::{Error, Result};
 use libbpf_sys::{bpf_map_update_elem, bpf_obj_get};
 use log::info;
 use std::{ffi::CString, os::raw::c_void};
-
-use crate::num_possible_cpus;
+use crate::{num_possible_cpus, linux::map_txq_config_base_setup};
 
 //* Provides an interface for querying the number of CPUs eBPF can
 //* see, and marking CPUs as available. Currently marks ALL eBPF
@@ -72,14 +71,7 @@ impl CpuMapping {
   }
 
   pub(crate) fn setup_base_txq_config(&self) -> Result<()> {
-    use crate::lqos_kernel::bpf::map_txq_config_base_setup;
-    // Should we shell out to the C and do it the easy way?
-    let result = unsafe { map_txq_config_base_setup(self.fd_txq_config) };
-    if !result {
-      Err(Error::msg("Unable to setup TXQ map"))
-    } else {
-      Ok(())
-    }
+    Ok(map_txq_config_base_setup(self.fd_txq_config)?)
   }
 }
 

src/rust/lqos_sys/src/linux/mod.rs

@@ -1,4 +1,6 @@
 //! Ports of C code that is very Linux specific.
 
 mod possible_cpus;
-pub use possible_cpus::num_possible_cpus;
+mod txq_base_setup;
+pub use possible_cpus::num_possible_cpus;
+pub(crate) use txq_base_setup::*;

src/rust/lqos_sys/src/linux/txq_base_setup.rs

@@ -0,0 +1,51 @@
+use std::ffi::c_void;
+use libbpf_sys::bpf_map_update_elem;
+use log::error;
+use thiserror::Error;
+use crate::num_possible_cpus;
+
+#[derive(Default)]
+#[repr(C)]
+struct TxqConfig {
+	/* lookup key: __u32 cpu; */
+	queue_mapping: u16,
+	htb_major: u16,
+}
+
+pub fn map_txq_config_base_setup(map_fd: i32) -> Result<(), MapTxqConfigError> {
+    let possible_cpus = num_possible_cpus().map_err(|_| MapTxqConfigError::NumCpusError)?;
+    if map_fd < 0 {
+        error!("ERR: (bad map_fd:{map_fd}) cannot proceed without access to txq_config map");
+        return Err(MapTxqConfigError::BadMapFd);
+    }
+
+    let mut txq_cfg = TxqConfig::default();
+    for cpu in 0 .. possible_cpus {
+        let cpu_u16: u16 = cpu as u16;
+        txq_cfg.queue_mapping = cpu_u16 + 1;
+		txq_cfg.htb_major     = cpu_u16 + 1;
+
+        let key_ptr: *const u32 = &cpu;
+        let val_ptr: *const TxqConfig = &txq_cfg;
+
+        let err = unsafe {
+            bpf_map_update_elem(map_fd, key_ptr as *const c_void, val_ptr as *mut c_void, 0)
+        };
+        if err != 0 {
+            error!("Unable to update TXQ map");
+            return Err(MapTxqConfigError::BpfMapUpdateFail);
+        }
+    }
+
+    Ok(())
+}
+
+#[derive(Error, Debug)]
+pub enum MapTxqConfigError {
+    #[error("Unable to determine number of CPUs")]
+    NumCpusError,
+    #[error("Bad Mapped File Descriptor")]
+    BadMapFd,
+    #[error("Unable to insert into map")]
+    BpfMapUpdateFail,
+}