ushcpc: gracefully handle packets with CHECKSUM_PARTIAL

function                                             old     new   delta
udhcp_recv_raw_packet                                415     579    +164
change_listen_mode                                   317     370     +53
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 217/0)             Total: 217 bytes

Signed-off-by: Alexey Froloff <raorn@raorn.name>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 49 insertions, 8 deletions

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index bc1db7087..dcb7d42dc 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -26,8 +26,8 @@
 #include "dhcpc.h"
 
 #include <netinet/if_ether.h>
-#include <netpacket/packet.h>
 #include <linux/filter.h>
+#include <linux/if_packet.h>
 
 /* "struct client_config_t client_config" is in bb_common_bufsiz1 */
 
@@ -836,12 +836,31 @@ static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
         int bytes;
         struct ip_udp_dhcp_packet packet;
         uint16_t check;
+        unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
+        struct iovec iov;
+        struct msghdr msg;
+        struct cmsghdr *cmsg;
 
-        bytes = safe_read(fd, &packet, sizeof(packet));
-        if (bytes < 0) {
-                log1("Packet read error, ignoring");
-                /* NB: possible down interface, etc. Caller should pause. */
-                return bytes; /* returns -1 */
+        /* used to use just safe_read(fd, &packet, sizeof(packet))
+         * but we need to check for TP_STATUS_CSUMNOTREADY :(
+         */
+        iov.iov_base = &packet;
+        iov.iov_len = sizeof(packet);
+        memset(&msg, 0, sizeof(msg));
+        msg.msg_iov = &iov;
+        msg.msg_iovlen = 1;
+        msg.msg_control = cmsgbuf;
+        msg.msg_controllen = sizeof(cmsgbuf);
+        for (;;) {
+                bytes = recvmsg(fd, &msg, 0);
+                if (bytes < 0) {
+                        if (errno == EINTR)
+                                continue;
+                        log1("Packet read error, ignoring");
+                        /* NB: possible down interface, etc. Caller should pause. */
+                        return bytes; /* returns -1 */
+                }
+                break;
         }
 
         if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
@@ -878,6 +897,20 @@ static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
                 return -2;
         }
 
+        for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+                if (cmsg->cmsg_level == SOL_PACKET
+                 && cmsg->cmsg_type == PACKET_AUXDATA
+                ) {
+                        /* some VMs don't checksum UDP and TCP data
+                         * they send to the same physical machine,
+                         * here we detect this case:
+                         */
+                        struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
+                        if (aux->tp_status & TP_STATUS_CSUMNOTREADY)
+                                goto skip_udp_sum_check;
+                }
+        }
+
         /* verify UDP checksum. IP header has to be modified for this */
         memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
         /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
@@ -888,6 +921,7 @@ static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd)
                 log1("Packet with bad UDP checksum received, ignoring");
                 return -2;
         }
+ skip_udp_sum_check:
 
         if (packet.data.cookie != htonl(DHCP_MAGIC)) {
                 bb_info_msg("Packet with bad magic, ignoring");
@@ -983,7 +1017,7 @@ static int udhcp_raw_socket(int ifindex)
         log1("Opening raw socket on ifindex %d", ifindex); //log2?
 
         fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
-        log1("Got raw socket fd %d", fd); //log2?
+        log1("Got raw socket fd"); //log2?
 
         sock.sll_family = AF_PACKET;
         sock.sll_protocol = htons(ETH_P_IP);
@@ -995,7 +1029,14 @@ static int udhcp_raw_socket(int ifindex)
                 /* Ignoring error (kernel may lack support for this) */
                 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
                                 sizeof(filter_prog)) >= 0)
-                        log1("Attached filter to raw socket fd %d", fd); // log?
+                        log1("Attached filter to raw socket fd"); // log?
+        }
+
+        if (setsockopt(fd, SOL_PACKET, PACKET_AUXDATA,
+                        &const_int_1, sizeof(int)) < 0
+        ) {
+                if (errno != ENOPROTOOPT)
+                        log1("Can't set PACKET_AUXDATA on raw socket");
         }
 
         log1("Created raw socket");