more httpraw bug fixes (#160)

* more httpraw bug fixes

* add http-linux example and add httpraw.Header.SetInt

* finish http-linux example

* fix CI vet

examples/http-linux/conn-linux.go

@@ -0,0 +1,96 @@
+//go:build !tinygo && linux
+
+package main
+
+import (
+	"net/netip"
+	"syscall"
+)
+
+// Conn wraps an accepted TCP connection from a raw Linux socket file descriptor.
+// It implements io.Reader/io.Writer/io.Closer over syscall.Read/Write/Close.
+type Conn struct {
+	fd     int
+	remote netip.AddrPort
+}
+
+// Read reads bytes from the connection into b.
+func (c *Conn) Read(b []byte) (int, error) {
+	if len(b) == 0 {
+		return 0, nil
+	}
+	n, err := syscall.Read(c.fd, b)
+	if err != nil {
+		return 0, err
+	}
+	if n == 0 {
+		return 0, syscall.ECONNRESET // Peer closed.
+	}
+	return n, nil
+}
+
+// Write writes b to the connection, looping until all bytes are sent.
+func (c *Conn) Write(b []byte) (int, error) {
+	total := 0
+	for total < len(b) {
+		n, err := syscall.Write(c.fd, b[total:])
+		if err != nil {
+			return total, err
+		}
+		total += n
+	}
+	return total, nil
+}
+
+// Close closes the underlying file descriptor.
+func (c *Conn) Close() error {
+	return syscall.Close(c.fd)
+}
+
+// RemoteAddr returns the peer address of the connection.
+func (c *Conn) RemoteAddr() netip.AddrPort { return c.remote }
+
+// Listener wraps a listening TCP socket bound to a local port.
+type Listener struct {
+	fd int
+}
+
+// Listen creates a listening TCP socket bound to port on all interfaces.
+func Listen(port uint16) (*Listener, error) {
+	fd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
+	if err != nil {
+		return nil, err
+	}
+	// Allow quick rebind after restart.
+	if err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1); err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+	addr := &syscall.SockaddrInet4{Port: int(port)}
+	if err = syscall.Bind(fd, addr); err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+	if err = syscall.Listen(fd, syscall.SOMAXCONN); err != nil {
+		syscall.Close(fd)
+		return nil, err
+	}
+	return &Listener{fd: fd}, nil
+}
+
+// Accept blocks until an incoming connection arrives and returns it as a Conn.
+func (l *Listener) Accept(conn *Conn) error {
+	nfd, sa, err := syscall.Accept(l.fd)
+	if err != nil {
+		return err
+	}
+
+	conn.fd = nfd
+	if sa4, ok := sa.(*syscall.SockaddrInet4); ok {
+		conn.remote = netip.AddrPortFrom(netip.AddrFrom4(sa4.Addr), uint16(sa4.Port))
+	}
+	return nil
+}
+
+// Close closes the listening socket.
+func (l *Listener) Close() error { return syscall.Close(l.fd) }