[Xen-changelog] [qemu-upstream-unstable] rtl8139: avoid nested ifs in IP header parsing

[patchbot@xxxxxxx]

commit 4b47e318c956c6cf7287870bf88cd306c1e4c068
Author:     Stefan Hajnoczi <stefanha@xxxxxxxxxx>
AuthorDate: Wed Jul 15 18:16:58 2015 +0100
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
CommitDate: Mon Aug 3 13:52:05 2015 +0000

    rtl8139: avoid nested ifs in IP header parsing
    
    Transmit offload needs to parse packet headers.  If header fields have
    unexpected values the offload processing is skipped.
    
    The code currently uses nested ifs because there is relatively little
    input validation.  The next patches will add missing input validation
    and a goto label is more appropriate to avoid deep if statement nesting.
    
    Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
    Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
 hw/net/rtl8139.c |   41 ++++++++++++++++++++++-------------------
 1 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c
index 5f0197c..91ba33b 100644
--- a/hw/net/rtl8139.c
+++ b/hw/net/rtl8139.c
@@ -2174,28 +2174,30 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s)
             size_t   eth_payload_len  = 0;
 
             int proto = be16_to_cpu(*(uint16_t *)(saved_buffer + 12));
-            if (proto == ETH_P_IP)
+            if (proto != ETH_P_IP)
             {
-                DPRINTF("+++ C+ mode has IP packet\n");
-
-                /* not aligned */
-                eth_payload_data = saved_buffer + ETH_HLEN;
-                eth_payload_len  = saved_size   - ETH_HLEN;
-
-                ip = (ip_header*)eth_payload_data;
-
-                if (IP_HEADER_VERSION(ip) != IP_HEADER_VERSION_4) {
-                    DPRINTF("+++ C+ mode packet has bad IP version %d "
-                        "expected %d\n", IP_HEADER_VERSION(ip),
-                        IP_HEADER_VERSION_4);
-                    ip = NULL;
-                } else {
-                    hlen = IP_HEADER_LENGTH(ip);
-                    ip_protocol = ip->ip_p;
-                    ip_data_len = be16_to_cpu(ip->ip_len) - hlen;
-                }
+                goto skip_offload;
             }
 
+            DPRINTF("+++ C+ mode has IP packet\n");
+
+            /* not aligned */
+            eth_payload_data = saved_buffer + ETH_HLEN;
+            eth_payload_len  = saved_size   - ETH_HLEN;
+
+            ip = (ip_header*)eth_payload_data;
+
+            if (IP_HEADER_VERSION(ip) != IP_HEADER_VERSION_4) {
+                DPRINTF("+++ C+ mode packet has bad IP version %d "
+                    "expected %d\n", IP_HEADER_VERSION(ip),
+                    IP_HEADER_VERSION_4);
+                goto skip_offload;
+            }
+
+            hlen = IP_HEADER_LENGTH(ip);
+            ip_protocol = ip->ip_p;
+            ip_data_len = be16_to_cpu(ip->ip_len) - hlen;
+
             if (ip)
             {
                 if (txdw0 & CP_TX_IPCS)
@@ -2391,6 +2393,7 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s)
             }
         }
 
+skip_offload:
         /* update tally counter */
         ++s->tally_counters.TxOk;
 
--
generated by git-patchbot for /home/xen/git/qemu-upstream-unstable.git

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