Commit 3d090aef authored by Andrew Oates's avatar Andrew Oates Committed by Samuel Thibault
Browse files

slirp: fix ICMP handling on macOS hosts 



On Linux, SOCK_DGRAM+IPPROTO_ICMP sockets give only the ICMP packet when
read from.  On macOS, however, the socket acts like a SOCK_RAW socket
and includes the IP header as well.

This change strips the extra IP header from the received packet on macOS
before sending it to the guest.  SOCK_DGRAM ICMP sockets aren't
supported on other BSDs, but we enable this behavior for them as well to
treat the sockets the same as raw sockets.

Signed-off-by: default avatarAndrew Oates <aoates@google.com>
Signed-off-by: default avatarSamuel Thibault <samuel.thibault@ens-lyon.org>
parent 632dd719

slirp/ip_icmp.c

+26 −1
Original line number Diff line number Diff line
@@ -420,7 +420,32 @@ void icmp_receive(struct socket *so) 
    icp = mtod(m, struct icmp *);



    id = icp->icmp_id;

    len = qemu_recv(so->s, icp, m->m_len, 0);

    len = qemu_recv(so->s, icp, M_ROOM(m), 0);

    /*

     * The behavior of reading SOCK_DGRAM+IPPROTO_ICMP sockets is inconsistent

     * between host OSes.  On Linux, only the ICMP header and payload is

     * included.  On macOS/Darwin, the socket acts like a raw socket and

     * includes the IP header as well.  On other BSDs, SOCK_DGRAM+IPPROTO_ICMP

     * sockets aren't supported at all, so we treat them like raw sockets.  It

     * isn't possible to detect this difference at runtime, so we must use an

     * #ifdef to determine if we need to remove the IP header.

     */

#ifdef CONFIG_BSD

    if (len >= sizeof(struct ip)) {

        struct ip *inner_ip = mtod(m, struct ip *);

        int inner_hlen = inner_ip->ip_hl << 2;

        if (inner_hlen > len) {

            len = -1;

            errno = -EINVAL;

        } else {

            len -= inner_hlen;

            memmove(icp, (unsigned char *)icp + inner_hlen, len);

        }

    } else {

      len = -1;

      errno = -EINVAL;

    }

#endif

    icp->icmp_id = id;



    m->m_data -= hlen;