From 8559a5f216947c1b6ed847b32124a9266b629be1 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 15 Jul 2015 18:16:58 +0100 Subject: [PATCH] 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 --- hw/rtl8139.c | 41 ++++++++++++++++++++++------------------- 1 file changed, 22 insertions(+), 19 deletions(-) diff --git a/hw/rtl8139.c b/hw/rtl8139.c index e3aa8bfb11..040caf19e0 100644 --- a/hw/rtl8139.c +++ b/hw/rtl8139.c @@ -2150,28 +2150,30 @@ 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) @@ -2367,6 +2369,7 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s) } } +skip_offload: /* update tally counter */ ++s->tally_counters.TxOk; -- 2.39.5