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slirp: fix ICMP handling on macOS hosts

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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>
This commit is contained in:
Andrew Oates 2018-08-15 20:18:45 -04:00 committed by Samuel Thibault
parent 632dd719b3
commit 3d090aefe2
1 changed files with 26 additions and 1 deletions
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27
slirp/ip_icmp.c
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@ -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;