more Linux specific options, skipping multicast ones

Author: avsm

lib_eio_linux/low_level.ml

@@ -647,6 +647,14 @@ module Sockopt = struct
   let ip_freebind = 15       (* IP_FREEBIND *)
   let ip_bind_address_no_port = 24  (* IP_BIND_ADDRESS_NO_PORT *)
   let ip_local_port_range = 51      (* IP_LOCAL_PORT_RANGE *)
+  let ip_ttl = 2             (* IP_TTL *)
+  let ip_mtu = 14            (* IP_MTU *)
+  let ip_mtu_discover = 10   (* IP_MTU_DISCOVER *)
+  (* IP_MTU_DISCOVER values *)
+  let ip_pmtudisc_want = 1   (* IP_PMTUDISC_WANT *)
+  let ip_pmtudisc_dont = 0   (* IP_PMTUDISC_DONT *)
+  let ip_pmtudisc_do = 2     (* IP_PMTUDISC_DO *)
+  let ip_pmtudisc_probe = 3  (* IP_PMTUDISC_PROBE *)
 
   external setsockopt_int : Unix.file_descr -> int -> int -> int -> unit = "caml_eio_sockopt_int_set"
   external getsockopt_int : Unix.file_descr -> int -> int -> int = "caml_eio_sockopt_int_get"
@@ -671,6 +679,9 @@ module Sockopt = struct
     | IP_FREEBIND : bool Eio.Net.Sockopt.t
     | IP_BIND_ADDRESS_NO_PORT : bool Eio.Net.Sockopt.t
     | IP_LOCAL_PORT_RANGE : (int * int) Eio.Net.Sockopt.t
+    | IP_TTL : int Eio.Net.Sockopt.t
+    | IP_MTU : int Eio.Net.Sockopt.t
+    | IP_MTU_DISCOVER : [`Want | `Dont | `Do | `Probe] Eio.Net.Sockopt.t
 
   let set : type a. Fd.t -> a Eio.Net.Sockopt.t -> a -> unit = fun fd opt v ->
     match opt with
@@ -754,6 +765,22 @@ module Sockopt = struct
       let combined = (upper lsl 16) lor lower in
       Fd.use_exn "setsockopt" fd (fun fd ->
         setsockopt_int fd ipproto_ip ip_local_port_range combined)
+    | IP_TTL ->
+      if v < 1 || v > 255 then
+        invalid_arg (Printf.sprintf "IP_TTL must be between 1 and 255, got %d" v);
+      Fd.use_exn "setsockopt" fd (fun fd ->
+        setsockopt_int fd ipproto_ip ip_ttl v)
+    | IP_MTU ->
+      invalid_arg "IP_MTU is a read-only socket option"
+    | IP_MTU_DISCOVER ->
+      let intval = match v with
+        | `Want -> ip_pmtudisc_want
+        | `Dont -> ip_pmtudisc_dont
+        | `Do -> ip_pmtudisc_do
+        | `Probe -> ip_pmtudisc_probe
+      in
+      Fd.use_exn "setsockopt" fd (fun fd ->
+        setsockopt_int fd ipproto_ip ip_mtu_discover intval)
     | _ -> Eio_unix.Net.Sockopt.set fd opt v
 
   let get : type a. Fd.t -> a Eio.Net.Sockopt.t -> a = fun fd opt ->
@@ -811,5 +838,20 @@ module Sockopt = struct
         let lower = combined land 0xFFFF in
         let upper = (combined lsr 16) land 0xFFFF in
         (lower, upper))
+    | IP_TTL ->
+      Fd.use_exn "getsockopt" fd (fun fd ->
+        getsockopt_int fd ipproto_ip ip_ttl)
+    | IP_MTU ->
+      Fd.use_exn "getsockopt" fd (fun fd ->
+        getsockopt_int fd ipproto_ip ip_mtu)
+    | IP_MTU_DISCOVER ->
+      let intval = Fd.use_exn "getsockopt" fd (fun fd ->
+        getsockopt_int fd ipproto_ip ip_mtu_discover)
+      in
+      if intval = ip_pmtudisc_want then `Want
+      else if intval = ip_pmtudisc_dont then `Dont
+      else if intval = ip_pmtudisc_do then `Do
+      else if intval = ip_pmtudisc_probe then `Probe
+      else failwith (Printf.sprintf "Unknown IP_MTU_DISCOVER value: %d" intval)
     | _ -> Eio_unix.Net.Sockopt.get fd opt
 end

lib_eio_linux/low_level.mli

@@ -253,6 +253,18 @@ module Sockopt : sig
         (** Set the per-socket local port range as (lower_bound, upper_bound).
             Both bounds are inclusive and must be in range 0-65535.
             Use (0, 0) to reset to system defaults. *)
+    | IP_TTL : int Eio.Net.Sockopt.t
+        (** Set or retrieve the time-to-live field used in every packet sent from this socket.
+            Valid range is 1-255. *)
+    | IP_MTU : int Eio.Net.Sockopt.t
+        (** Retrieve the current known path MTU of the current socket.
+            Only valid for connected sockets. This is a read-only option. *)
+    | IP_MTU_DISCOVER : [`Want | `Dont | `Do | `Probe] Eio.Net.Sockopt.t
+        (** Set or receive the Path MTU Discovery setting for a socket.
+            - [`Want]: Use per-route settings (fragment if needed)
+            - [`Dont]: Never do Path MTU Discovery
+            - [`Do]: Always do Path MTU Discovery (reject large datagrams with EMSGSIZE)
+            - [`Probe]: Set DF but ignore Path MTU (for diagnostic tools) *)
 
   val set : fd -> 'a Eio.Net.Sockopt.t -> 'a -> unit
   (** [set fd opt v] sets socket option [opt] to value [v] on file descriptor [fd]. *)

lib_eio_linux/tests/network.md

@@ -209,6 +209,44 @@ Test that invalid values are rejected properly:
       ELS.set fd ELS.TCP_LINGER2 None;
       traceln "TCP_LINGER2 accepts None for system default";
 
+      (* Test IP_TTL *)
+      ELS.set fd ELS.IP_TTL 64;
+      let ttl = ELS.get fd ELS.IP_TTL in
+      traceln "IP_TTL: %d" ttl;
+
+      (* Test IP_TTL validation *)
+      (try
+        ELS.set fd ELS.IP_TTL 0;
+        traceln "ERROR: IP_TTL accepted value 0"
+      with Invalid_argument msg ->
+        traceln "IP_TTL zero check: %s" msg);
+
+      (try
+        ELS.set fd ELS.IP_TTL 256;
+        traceln "ERROR: IP_TTL accepted value 256"
+      with Invalid_argument msg ->
+        traceln "IP_TTL overflow check: %s" msg);
+
+      (* Test IP_MTU_DISCOVER *)
+      ELS.set fd ELS.IP_MTU_DISCOVER `Dont;
+      let mtu_disc = ELS.get fd ELS.IP_MTU_DISCOVER in
+      traceln "IP_MTU_DISCOVER: %s" (match mtu_disc with
+        | `Want -> "Want"
+        | `Dont -> "Dont"
+        | `Do -> "Do"
+        | `Probe -> "Probe");
+
+      (* Test IP_MTU (read-only, should work on connected socket) *)
+      let mtu = ELS.get fd ELS.IP_MTU in
+      traceln "IP_MTU: %d bytes" mtu;
+
+      (* Test that IP_MTU cannot be set *)
+      (try
+        ELS.set fd ELS.IP_MTU 1500;
+        traceln "ERROR: IP_MTU allowed setting (should be read-only)"
+      with Invalid_argument msg ->
+        traceln "IP_MTU set validation: %s" msg);
+
       (* Test IP_LOCAL_PORT_RANGE validation *)
       (try
         (* Lower bound > upper bound *)
@@ -245,6 +283,12 @@ Test that invalid values are rejected properly:
 +TCP_WINDOW_CLAMP validation: TCP_WINDOW_CLAMP must be non-negative, got -100
 +TCP_LINGER2 validation: TCP_LINGER2 must be non-negative, got -2
 +TCP_LINGER2 accepts None for system default
++IP_TTL: 64
++IP_TTL zero check: IP_TTL must be between 1 and 255, got 0
++IP_TTL overflow check: IP_TTL must be between 1 and 255, got 256
++IP_MTU_DISCOVER: Dont
++IP_MTU: 65535 bytes
++IP_MTU set validation: IP_MTU is a read-only socket option
 +IP_LOCAL_PORT_RANGE validation: IP_LOCAL_PORT_RANGE lower bound (2000) must be <= upper bound (1000)
 +IP_LOCAL_PORT_RANGE upper bound check: IP_LOCAL_PORT_RANGE upper bound must be 0-65535, got 70000
 +IP_LOCAL_PORT_RANGE accepts valid range 40000-50000