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: Andrew Oates <aoates@google.com> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
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@ -420,7 +420,32 @@ void icmp_receive(struct socket *so)
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icp = mtod(m, struct icmp *);
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id = icp->icmp_id;
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len = qemu_recv(so->s, icp, m->m_len, 0);
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len = qemu_recv(so->s, icp, M_ROOM(m), 0);
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/*
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* The behavior of reading SOCK_DGRAM+IPPROTO_ICMP sockets is inconsistent
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* between host OSes. On Linux, only the ICMP header and payload is
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* included. On macOS/Darwin, the socket acts like a raw socket and
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* includes the IP header as well. On other BSDs, SOCK_DGRAM+IPPROTO_ICMP
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* sockets aren't supported at all, so we treat them like raw sockets. It
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* isn't possible to detect this difference at runtime, so we must use an
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* #ifdef to determine if we need to remove the IP header.
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*/
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#ifdef CONFIG_BSD
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if (len >= sizeof(struct ip)) {
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struct ip *inner_ip = mtod(m, struct ip *);
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int inner_hlen = inner_ip->ip_hl << 2;
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if (inner_hlen > len) {
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len = -1;
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errno = -EINVAL;
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} else {
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len -= inner_hlen;
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memmove(icp, (unsigned char *)icp + inner_hlen, len);
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}
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} else {
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len = -1;
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errno = -EINVAL;
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}
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#endif
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icp->icmp_id = id;
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m->m_data -= hlen;
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