From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51695) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fq60v-0008Lt-D9 for qemu-devel@nongnu.org; Wed, 15 Aug 2018 20:19:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fq60q-0008Na-1l for qemu-devel@nongnu.org; Wed, 15 Aug 2018 20:19:45 -0400 Received: from mail-qk0-x242.google.com ([2607:f8b0:400d:c09::242]:40417) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fq60i-0008Kt-0x for qemu-devel@nongnu.org; Wed, 15 Aug 2018 20:19:37 -0400 Received: by mail-qk0-x242.google.com with SMTP id c126-v6so2159728qkd.7 for ; Wed, 15 Aug 2018 17:19:28 -0700 (PDT) Sender: Andrew Oates From: andrew@andrewoates.com Date: Wed, 15 Aug 2018 20:18:45 -0400 Message-Id: <20180816001845.29052-1-andrew@andrewoates.com> Subject: [Qemu-devel] [PATCH v4] slirp: fix ICMP handling on macOS hosts List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: peter.maydell@linaro.org, samuel.thibault@ens-lyon.org, jan.kiszka@siemens.com, qemu-devel@nongnu.org Cc: Andrew Oates From: Andrew Oates 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 --- v2: check validity of inner_hlen and update len appropriately v3: CONFIG_DARWIN -> CONFIG_BSD; add comment explaining #ifdef v4: drop packets that are too short for an IP header slirp/ip_icmp.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) diff --git a/slirp/ip_icmp.c b/slirp/ip_icmp.c index 0b667a429a..da100d1f55 100644 --- a/slirp/ip_icmp.c +++ b/slirp/ip_icmp.c @@ -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; -- 2.17.0